blower

Abstract

The blower includes: an impeller having a cylindrical hub rotatably driven by a motor and a plurality of blades radially arranged from the hub; a cylindrical air guide portion disposed so as to cover the outer peripheral ends of the plurality of blades and allow air to flow from one end of the air guide portion to the other end; and an annular bell mouth, disposed from a position downstream of one end of the air guide portion and upstream of the impeller to a position upstream of one end of the air guide portion, forming a first suction flow path within the bell mouth and a second suction flow path outside the bell mouth between the bell mouth and the inner surface of the bell mouth. The bell mouth has a minimum radius point in an area between an upstream end point of an inlet of the first suction flow path and a downstream end point of the bell mouth located at an outlet of the first suction flow path, wherein the minimum radius point is located at a smaller distance from the radial direction of the hub's rotation axis than the radial distance from the downstream end point to the hub's rotation axis.

Description

Technical Field

[0001] The present disclosure relates to a blower having a hub. Background Art

[0002] In a blower, for example, an axial flow blower or a diagonal flow blower, the blower has an impeller having a hub serving as a center of rotation and a plurality of blades arranged on the outer periphery of the hub. Such a blower is configured such that an impeller and a motor for driving the impeller are provided in a cylindrical casing, and the impeller is rotated by the motor, thereby sucking air from one side of the casing and discharging the air after passing through the impeller from the other side of the casing. Among such blowers, there is an axial flow blower in which an inner wall is arranged in front of the impeller so as to be located inside the casing and overlap with the casing, and a second suction path is formed between the inner surface of the casing and the inner wall (for example, refer to Patent Document 1). In the axial flow blower of Patent Document 1, the inner wall has a constant thickness, the downstream side of the inner wall is parallel to the inner surface of the casing, and the discharge opening on the impeller side of the second suction path faces the downstream side in the axial direction. In addition, in the axial flow blower of Patent Document 1, the side end edge of the inner wall on the suction side is formed into a bell-mouth shape, and the suction opening of the second suction path opposite to the impeller is located upstream of the casing and faces outward in the radial direction of the casing.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 3491342 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] According to the axial flow blower of Patent Document 1, the airflow that passes through the second suction path and flows into the housing can be used to suppress the generation of leakage flow toward the upstream side at the outer peripheral end of the blade, and the noise generated between the impeller and the inner surface of the housing can be suppressed. However, since the inner wall (bell mouth) of the axial flow blower of Patent Document 1 is parallel to the inner surface of the housing near the discharge opening, the airflow after passing through the main flow path and the second suction path is discharged in the axial direction and goes straight to the downstream side. Therefore, the airflow discharged from the main flow path and the airflow discharged from the discharge opening of the second suction path sometimes interfere with the outer peripheral part of the blade, and the noise suppression effect and air supply performance are sometimes reduced. In particular, in a structure where the outer peripheral end of the blade is located radially outward of the lower end of the inner wall, as in the axial flow blower disclosed in Patent Document 1, the possibility of the airflow interfering with the outer peripheral part of the blade becomes higher, and the noise suppression effect and air supply performance are sometimes reduced.

[0008] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide an air blower capable of improving the noise suppression effect and suppressing a decrease in air blowing performance.

[0009] Means for solving problems

[0010] The blower of the present disclosure includes: an impeller having a cylindrical hub rotatably driven by a motor and a plurality of blades radially arranged from the hub; a cylindrical air guide portion provided so as to cover the outer peripheral ends of the plurality of blades and to allow air flow to flow from one end of the air guide portion to the other end; and an annular bell mouth provided from a position downstream of the one end of the air guide portion and upstream of the impeller to a position upstream of the one end of the air guide portion, forming a first suction flow path inside the bell mouth and a second suction flow path outside the bell mouth between the bell mouth and the inner surface of the air guide portion, the bell mouth having a minimum radius point in a section between an upstream end point located at an inlet of the first suction flow path and a downstream end point of the bell mouth located at an outlet of the first suction flow path, the minimum radius point being smaller in radial direction from the rotation axis of the hub than the radial direction from the downstream end point to the rotation axis of the hub.

[0011] Effects of the Invention

[0012] According to the present disclosure, since the minimum radius point exists between the upstream and downstream endpoints of the bell mouth, the airflow near the downstream endpoint has a radially outward component, and the airflow discharged toward the impeller has a peripheral component. This makes it less likely that the airflow discharged from the second intake flow path will interfere with the outer periphery of the blades compared to conventional methods, and the amount of air flowing through the gap between the blades and the air guide can be increased compared to conventional methods. This improves noise suppression and minimizes degradation in air supply performance compared to conventional methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a perspective view showing an impeller of the air blower according to Embodiment 1.

[0014] Figure 2 This is a schematic diagram showing a radial cross section of the air blower according to the first embodiment.

[0015] Figure 3 yes Figure 2 A partial enlarged view of .

[0016] Figure 4 It shows Figure 3 A schematic diagram of a modified example of the bell mouth of the blower.

[0017] Figure 5 It shows Figure 4 Chart showing the relationship between the flow coefficient and the specific noise (in Japanese: 比騒音) in the blower

[0018] Figure 6 It is a schematic partial enlarged view showing the radial cross-section of the blower of Embodiment 2.

[0019] Figure 7 It is a schematic partial enlarged view showing the radial cross-section of the blower of Embodiment 3.

[0020] Figure 8 It is a schematic partial enlarged view showing the radial cross-section of the blower of Embodiment 4.

[0021] Figure 9 It is a schematic partial enlarged view showing the radial cross-section of the blower of Embodiment 5.

[0022] Figure 10 It is to Figure 9 The schematic diagram obtained by projecting and unfolding the cylindrical cross-section at A-A' of Detailed implementation mode

[0023] Embodiment 1.

[0024] Figure 1 It is a perspective view showing the impeller 1 of the blower of Embodiment 1. Figure 2 It is a schematic diagram showing the radial cross-section of the blower 100 of Embodiment 1. Specifically, in Figure 2 It shows a cross-sectional view obtained by rotating and projecting the cross-section of the blower 100 including the rotating shaft RS on a plane parallel to the rotating shaft RS. Based on Figure 1 and Figure 2 , the structure of the blower 100 will be described.

[0025] As Figure 2 shown, the blower 100 has a housing 4 and an impeller 1 disposed within the housing 4. In addition, the blower 100 includes a motor not shown. The blower 100 is, for example, an axial-flow blower. In Figure 1 the example shown, as the impeller 1, a propeller fan is provided. As Figure 1 shown, the impeller 1 is composed of a hub 2 having a substantially cylindrical shape (including a frustum of a cone shape) and a plurality of blades 3 mounted on the outer periphery of the hub 2. The motor not shown is connected to the hub 2 and disposed inside or on the downstream side of the hub 2. The hub 2 is rotationally driven about the rotating shaft RS by the motor. In the figure, the rotation direction of the impeller 1 is indicated by an arrow R, and the direction of the air flow sucked into the impeller 1 is indicated by a hollow arrow F. The impeller 1 sucks the air flow along the axial direction of the rotating shaft RS (the direction of the arrow F) and discharges the air flow along the axial direction of the rotating shaft RS (the direction of the arrow F).

[0026] (Blade 3)

[0027] A plurality of blades 3 are radially arranged from the hub 2 toward the radially outer side. Figure 1 , the number of blades 3 is not particularly limited to seven. Each blade 3 has a predetermined three-dimensional shape. The blade 3 is composed of a forward blade with a blade leading edge 31 extending forward in the direction of rotation (the direction of arrow R).

[0028] (Wheel Hub 2)

[0029] A central portion of the hub 2 is connected to a motor (not shown), and the impeller 1 is rotated by the driving force of the motor.

[0030] (Shell 4)

[0031] like Figure 2 As shown, the housing 4 includes a cylindrical air guide portion 6 covering the outer periphery of the impeller 1, i.e., the outer peripheral ends 3e of the plurality of blades 3, and an annular bell mouth 5 for guiding air into the air guide portion 6. In addition, the housing 4 includes a flange portion 12 provided continuously with the bell mouth 5.

[0032] (Air guide portion 6)

[0033] The air guide portion 6 has, for example, a cylindrical shape. The impeller 1 is arranged in the air guide portion 6 so that the axis of the air guide portion 6 is aligned with the rotation axis RS of the impeller 1. The air flow is sucked into the air guide portion 6 from one end on the upstream side of the air guide portion 6, and the air flow passes through the impeller 1 and is discharged from the other end on the downstream side of the air guide portion 6. That is, in the direction of the air flow passing through the impeller 1 (the direction of the arrow F), the suction-side opening 6a of the air guide portion 6 is located on the upstream side, and the discharge-side opening 6b of the air guide portion 6 is located on the downstream side, and the air flow flows from one end to the other end of the air guide portion 6. In the following description, the most upstream portion of the air guide portion 6 is referred to as the upstream end point U1.

[0034] exist Figure 2 In the example shown, the air guide 6 consists solely of a straight pipe portion whose inner diameter, i.e., the distance between the inner surface 61 of the air guide 6 and the rotation axis RS, is constant from the suction-side opening 6a to the discharge-side opening 6b. The shape of the air guide 6 is not limited to this. For example, the air guide 6 may be composed of a combination of a straight pipe portion covering the outer circumference of the impeller 1, a constricted pipe portion whose inner diameter gradually decreases toward the downstream side, and an expanded pipe portion whose inner diameter gradually increases toward the downstream side. Furthermore, when using a diagonal flow impeller 1, the air guide 6 may consist solely of an expanded pipe portion whose diameter gradually increases toward the downstream side, such as a hollow truncated cone.

[0035] (Bell 5)

[0036] The bell mouth 5 has a cylindrical shape with a varying inner diameter in the axial direction of the rotation axis RS. The bell mouth 5 is positioned near the suction-side opening 6a of the air guide 6 so as to partially overlap the air guide 6 in the axial direction of the rotation axis RS. More specifically, the bell mouth 5 is positioned from a position downstream of the suction-side opening 6a of the air guide 6 and upstream of the impeller 1 to a position upstream of the suction-side opening 6a of the air guide 6. The bell mouth 5 is positioned so that its central axis coincides with the rotation axis RS of the impeller 1 and the central axis of the air guide 6.

[0037] A first suction flow path 7 is formed within the bellmouth 5, and a second suction flow path 8 is formed between the bellmouth 5 and the inner surface 61 of the air guide 6. Specifically, the first suction flow path 7, which includes the rotation axis RS, is formed on the airflow suction side of the blower 100, and the second suction flow path 8 is formed on the outer periphery of the first suction flow path 7, with the bellmouth 5 as the boundary. In other words, the first suction flow path 7 is formed by the inner periphery 51 of the bellmouth 5, and the second suction flow path 8 is formed by the outer periphery 52 of the bellmouth 5 and the inner surface 61 of the air guide 6.

[0038] The bell mouth 5 is composed of, for example, a curved portion having a curved wall surface in the axial direction of the rotation axis RS. Figure 2 In the example shown, the bell mouth 5 has a circular arc shape with a generally uniform curvature from the airflow intake side to the airflow outlet side. In the following description, the point at the beginning of the curve in the bell mouth 5 and on the most upstream side of the bell mouth 5 is referred to as the upstream endpoint B0, and the point on the most downstream side of the bell mouth 5 is referred to as the downstream endpoint B1. Here, the upstream endpoint B0 and the downstream endpoint B1 are set on the inner circumferential surface 51 of the bell mouth 5.

[0039] Furthermore, the shape of the bell mouth 5 is not limited to the above-described shape. For example, the bell mouth 5 may be formed from an upstream endpoint B0 of the bell mouth 5 located at the inlet of the first suction flow path 7 to a downstream endpoint B1 of the bell mouth 5 located at the outlet of the first suction flow path 7, and may be composed of multiple curved portions. Alternatively, the bell mouth 5 may be formed by combining curved portions such as an expansion portion and a contraction portion with a straight portion. The curved portion of the bell mouth 5 may be a single arc shape or an elliptical shape, or may be a shape formed by combining arcs having multiple curvatures.

[0040] The inlet of the second suction flow path 8 is formed by the upstream end point U1 of the air guide portion 6 and a portion of the outer peripheral surface 52 of the bell mouth 5 that faces the upstream end point U1 of the air guide portion 6. The outlet of the second suction flow path 8 is formed by the downstream end point B1 of the bell mouth 5 and a portion of the inner surface 61 of the air guide portion 6 that faces the downstream end point B1 of the bell mouth 5.

[0041] The inlet of the second suction flow path 8 is provided to open radially outward, and the airflow heading radially inward passes through the inlet of the second suction flow path 8. On the other hand, the outlet of the second suction flow path 8 is provided to open downstream in the direction of the airflow passing through the impeller 1 (the direction of arrow F), and the airflow F1 containing the component heading downstream passes through the outlet of the second suction flow path 8. Here, heading downstream means advancing in the direction of arrow F parallel to the axial direction of the rotation axis RS.

[0042] The bell mouth 5 guides air whose upstream endpoint B0 is located near the inner circumferential surface 51 of the bell mouth 5 into the first intake flow path 7 through the inlet of the first intake flow path 7 and is then supplied to the downstream impeller 1. Furthermore, air whose upstream endpoint B0 is located near the outer circumferential surface 52 of the bell mouth 5 is guided into the second intake flow path 8 through the inlet of the second intake flow path 8, and is then turned and supplied to the gap 9 between the inner surface 61 of the air guide portion 6 and the outer circumferential ends 3e of the plurality of blades 3.

[0043] (Flange 12)

[0044] The flange portion 12 is provided on the outer periphery of the bell mouth 5, continuously with the upstream end point B0 of the bell mouth 5, and has a flat plate shape extending in a direction perpendicular to the rotation axis RS. The bell mouth 5 and the flange portion 12 are smoothly connected, for example, integrally formed. The flange portion 12 separates the upstream side of the inlet of the first suction flow path 7 from the upstream side of the inlet of the second suction flow path 8.

[0045] Reference Figure 2 , the flow of air in the blower 100 is described. The air flow Fi flowing from the upstream side of the bell mouth 5 through the first suction flow path 7 into the interior of the air guide 6 passes through the impeller 1. After a portion of the air flow (air flow Fo2) after passing through the impeller 1 is discharged from the discharge side opening 6b, it flows along the outer surface 62 of the air guide 6 (air flow F3) and flows into the air guide 6 again through the inlet of the second suction flow path 8. The air flow flowing into the second suction flow path 8 turns in the second suction flow path 8 and flows out through the outlet of the second suction flow path 8 (air flow F1). The air flow F1 flowing out of the second suction flow path 8 passes near the outer periphery of the impeller 1 and is discharged to the outside of the air guide 6 through the discharge side opening 6b of the air guide 6. At this time, the air flow F1 flowing out of the second suction flow path 8 is used to suppress the generation of the leakage flow F2 from the outer peripheral end 3e of the blade 3 toward the upstream side. On the other hand, the air flows into the interior of the air guide portion 6 (airflow Fi) through the first suction flow path 7, and the remaining part of the airflow (airflow Fo1) after passing through the impeller 1 is discharged axially to the outside of the air guide portion 6 through the discharge side opening 6b of the air guide portion 6.

[0046] As described above, in blower 100, the inlet portion that allows airflow into air guide 6 is configured to include a first intake flow path 7 for drawing in the main flow, and a second intake flow path 8 separated from the first intake flow path 7 by a bell mouth 5. Near the discharge-side opening 6b of air guide 6, which is the outlet side of the airflow in impeller 1, there is a region Ar2 that is higher in pressure than region Ar1, which is the inlet side of the airflow in impeller 1, near the outlet of first intake flow path 7. Furthermore, near the inlet of second intake flow path 8, where airflow F3 flows, there is also a region Ar3 that is higher in pressure than region Ar1.

[0047] Furthermore, the flange portion 12 is provided upstream of the inlet of the first intake passage 7 and the inlet of the second intake passage 8. This prevents mixing of air between area Ar1 and areas Ar2 and Ar3, which are higher pressure than area Ar1, thereby reducing the pressure difference. This prevents air from flowing from the first intake passage 7 and the outer peripheral ends 3e of the blades 3 into the second intake passage 8, suppressing leakage flow F2 through the impeller 1 and allowing efficient axial discharge. Furthermore, the outer peripheral airflow Fo2 of the airflow passing through the impeller 1 and discharged from the air guide 6, namely, the airflow F3 flowing along the outer surface 62 of the air guide 6, is guided by the flange portion 12 to the inlet of the second intake passage 8, forming a flow that flows into the second intake passage 8.

[0048] Figure 3 yes Figure 2 A partial enlarged view of the . Figure 3 , the positional relationship between the bell mouth 5 and the air guide 6 and the shape of the bell mouth 5 are described. The downstream end point B1 of the bell mouth 5 is located on the downstream side and inner peripheral side of the air flow relative to the upstream end point U1 of the air guide 6. Figure 3 In the illustrated example, the upstream end point B0 of the bell mouth 5 is located on the outer peripheral side and upstream of the airflow relative to the upstream end point U1 of the air guide portion 6 .

[0049] The bell mouth 5 has a shape in which the inner diameter of the bell mouth 5 gradually decreases as it moves away from the upstream end point B0, and gradually increases as it approaches the downstream end point B1, at the downstream end point B1. In other words, the bell mouth 5 has a shape in which the inner diameter gradually decreases from the upstream end point B0 to the downstream end point B1, and then gradually increases.

[0050] The bell mouth 5 only needs to have a structure where the downstream end portion 53 including the downstream end point B1 faces radially outward. In other words, the bell mouth 5 has a minimum radius point Bm between the upstream end point B0 and the downstream end point B1, whose radial distance from the rotation axis RS of the hub 2 is smaller than that of the downstream end point B1. That is, the radial distance R1 between the downstream end point B1 and the rotation axis RS and the radial distance R1min between the minimum radius point Bm and the rotation axis RS satisfy the relationship R1>R1min. Figure 3 In the example shown, the minimum radius point Bm is set on the inner circumferential surface 51 of the bell mouth 5. In addition, the radial distance R1min between the minimum radius point Bm of the bell mouth 5 and the rotation axis RS of the hub 2 is smaller than the radial distance between the upstream end point B0 of the bell mouth 5 and the rotation axis RS of the hub 2. The minimum radius point Bm of the bell mouth 5 is a point located radially inward of the upstream end point B0 and the downstream end point B1, indicating that the bell mouth 5 has a convex shape toward the inside. Figure 3 The portion of the bell mouth 5 that is closest to the rotation axis RS in the radial direction. The bell mouth 5 is arranged relative to the air guide 6 so that the minimum radius point Bm of the bell mouth 5 and the upstream end point U1 of the air guide 6 are approximately aligned in the axial direction.

[0051] exist Figure 3 In the example shown, the upstream endpoint B0, downstream endpoint B1, and minimum radius point Bm are set to indicate specific positions on the inner circumferential surface 51 of the bell mouth 5 that forms the first suction flow path 7. Furthermore, the bell mouth 5 is formed by bending a plate-like member of uniform thickness. This results in a structure in which the relationship R1 > R1min is satisfied, and the minimum radius point Bm, where the distance from the rotation axis RS is minimized, is located between the upstream endpoint B0 and the downstream endpoint B1 of the bell mouth 5.

[0052] In addition, Figure 3 In the example shown, the inner circumferential surface 51 of the wall portion of the bell mouth 5, extending from the minimum radius point Bm to the downstream end point B1, is formed in a curved shape such that the inner diameter of the bell mouth 5 gradually increases from the minimum radius point Bm to the downstream end point B1. Furthermore, the outer circumferential surface 52 is also formed in a curved shape along the inner circumferential surface 51, extending from the minimum radius point Bm to the downstream end point B1. Alternatively, the bell mouth 5 may be configured such that the portion extending from the minimum radius point Bm to the downstream end point B1 is connected in a straight line. However, to prevent separation of the airflow flowing near the bell mouth 5, it is preferred that the portion extending from the minimum radius point Bm to the downstream end point B1 be connected in a gentle curve.

[0053] As described above, the downstream end portion 53 of the bell mouth 5 is a structure facing radially outward. By such a structure, it is possible to suppress the air flow from passing through the gap 9. Figure 2The illustrated impeller 1 has a region Ar1 on the suction side and a region Ar2 on the discharge side mixed with each other. Therefore, the leakage flow F2 generated in the gap 9 can be suppressed, and the noise caused by the leakage flow F2 can be reduced.

[0054] Furthermore, for example, in a blower with a bellmouth integrally formed in the air guide and a single suction flow path at the inlet portion of the blower, the blades rotate relative to the rotation axis, generating leakage flow upstream from the outer periphery of the blades. Furthermore, this leakage flow interferes with the inner circumference of the bellmouth, sometimes causing turbulence in the airflow and increasing noise.

[0055] On the other hand, in the blower 100 of embodiment 1, since the bell mouth 5 and the air guide portion 6 are configured to partially overlap, the air flow F1 having a component toward the downstream side after passing through the second suction flow path 8 can be used to suppress the leakage flow F2 in the gap 9, thereby achieving noise reduction.

[0056] Furthermore, in the blower 100 of Embodiment 1, since the inner diameter of the bell mouth 5 gradually increases at the downstream end thereof, the airflow F1 after passing through the outlet of the second intake flow path 8 includes not only a component directed downstream but also a component directed radially outward. Consequently, since the airflow F1 after passing through the outlet of the second intake flow path 8 flows toward the outer periphery and downstream between the blades 3 and the air guide 6, interference between the airflow F1 and the outer periphery of the blades 3 can be reduced.

[0057] In conventional blowers, the downstream end of the bell mouth is formed parallel to the inner surface of the air guide portion. Therefore, the airflow F1 after passing through the second intake flow path is more likely to directly interfere with the blades. In particular, in a conventional configuration where the blower is projected axially so that the outer periphery of the blades 3 overlaps the outlet of the second intake flow path, the airflow F1 flowing out of the second intake flow path 8 directly interferes with the outer periphery of the blades.

[0058] Furthermore, in conventional blowers, the inlet of the first and second suction passages have approximately the same air pressure, and the downstream end of the bell mouth is formed parallel to the inner surface of the air guide. Consequently, in conventional blowers, air has difficulty flowing into the second suction passage, which is narrower than the first suction passage at the downstream end of the bell mouth, making it difficult to maintain the wind speed required to suppress leakage flow.

[0059] On the other hand, in the blower 100 of the first embodiment, as Figure 3As shown, the bell mouth 5 has a minimum radius point Bm between the upstream endpoint B0 and the downstream endpoint B1, where R1>R1min is satisfied. Therefore, in the bell mouth 5, the downstream endpoint B1 is radially outward of the minimum radius point Bm. The downstream end 53 of the bell mouth 5 functions as a diffuser, expanding the airflow Fi passing through the first intake passage 7 and toward the impeller 1 outward. Consequently, near the downstream end 53 of the bell mouth 5, the direction of the airflow discharged from the outlet of the first intake passage 7 is tilted outward compared to conventional methods. This reduces interference between the airflow discharged toward the impeller 1 and the wake formed downstream of the bell mouth 5 and the blades 3. Furthermore, the provision of the flange 12 increases the amount of airflow flowing into the second intake passage 8 and increases the velocity of the airflow passing through the second intake passage 8 compared to conventional blowers without the flange 12, thereby enhancing the effectiveness of suppressing the leakage flow F2.

[0060] Furthermore, in embodiment 1, as Figure 2 As shown, the shape of the downstream end of the bell mouth 5 suppresses mixing of airflow in area Ar1 at the outlet of the first intake passage and area Ar2 on the discharge side of the impeller 1 via the gap 9 between the blades 3 and the air guide 6. Consequently, area Ar2 on the discharge side of the impeller 1 and area Ar3 near the inlet of the second intake passage 8 are maintained at a higher pressure than area Ar1 at the outlet of the first intake passage, thereby facilitating airflow into the second intake passage 8. Consequently, a higher-speed airflow than conventionally discharged from the second intake passage 8 is effectively suppressed, even against the higher-speed leakage flow F2.

[0061] Figure 4 It shows Figure 3 A schematic diagram of a modified example of the bell mouth 5 of the blower. When the bell mouth 5 has a certain thickness, the thickness t of the bell mouth 5 can also be considered and the minimum radius point Bm is set at the middle point between the inner peripheral surface 51 and the outer peripheral surface 52, that is, the center of the thickness t. Figure 4 In the modified example shown, the thickness t of the bell mouth 5 is made thinner on the front end side, thereby satisfying the relationship R1>R1min. Figure 4 A method of defining the distance between the bell mouth 5 and the rotation axis RS in this case will be described.

[0062] exist Figure 4In the modified example shown, the bell mouth 5 is formed by bending a plate-like member having a tapered tip. The upstream end point B0, downstream end point B1, and minimum radius point Bm of the bell mouth 5 are set on the imaginary center line La of the thickness t of the bell mouth 5. The bell mouth 5 is formed so that the radial distance R1 between the downstream end point B1 of the bell mouth 5 and the rotation axis RS is greater than the radial distance R1min between the minimum radius point Bm of the bell mouth 5 and the rotation axis RS. Figure 4 In the figure, from the minimum radius point Bm of the bell mouth 5 to the downstream end point B1, the radial distance between the inner circumferential surface 51 and the rotation axis RS increases as it approaches the downstream side, while the radial distance dR between the outer circumferential surface 52 of the bell mouth 5, which overlaps with the air guide portion 6 in the axial direction, and the inner surface 61 of the air guide portion 6 is constant. The inner circumferential surface 51 of the bell mouth 5 is formed, for example, in the following curved shape: the inner diameter of the bell mouth 5 gradually increases from the minimum radius point Bm to the downstream end point B1.

[0063] In the bell mouth 5 of the modified example, the thickness t of the bell mouth 5 becomes thinner as it goes to the downstream side, and the inner peripheral surface 51 expands radially outward from the minimum radius point Bm toward the downstream end point B1. Figure 3 The example shown in FIG. 1 can also suppress the interference with the blade 3. In addition, in particular, as Figure 4 As shown, when the radial distance dR between the outer peripheral surface 52 of the bell mouth 5 and the inner surface 61 of the air guide portion 6 is constant, compared with the case where the outer peripheral surface 52 is set to a curved shape, undercut processing is not required during the forming process of the bell mouth 5, and manufacturing becomes easier.

[0064] Figure 5 It shows Figure 4 A graph showing the relationship between the flow coefficient φ and the specific noise Ks (dBA) in the blower 100. Figure 5 In the figure, the solid line g1 represents Figure 4 The results obtained by the blower 100 are shown as a comparative example. The results obtained by the blower 100 using a general duct type housing with a continuous air guide and a bell mouth are shown as a dotted line g2. Specifically, the solid line g1 is the result obtained by the blower 100 using Figure 4 The bell mouth 5 shown has a tapered front end, and the radial distance dR between the outer peripheral surface 52 of the bell mouth 5 and the inner surface 61 of the air guide 6 is smaller than the radial distance dRt between the outer peripheral end 3e of the blade 3 and the inner surface 61 of the air guide 6. Figure 4 The same impeller 1 is used in the blower 100 and the blower using a duct type casing. The flow coefficient φ is an indicator of the performance of the blower 100, which is determined by the air volume, the annular flow path area, and the circumferential speed of the blade tip.

[0065] according to Figure 5 When the flow coefficient φ is between 0.077 and 0.23, the level of the specific noise Ks (dBA) obtained by the blower 100 of embodiment 1 is lower than the level of the specific noise Ks (dBA) obtained by the blower using a duct type casing. Figure 5 It can be seen that the blower 100 using the casing 4 of Embodiment 1 can achieve a noise suppression effect over a wider range of flow rates when the flow coefficient φ is in the flow rate range of 0.077 to 0.23, compared to the blower using a duct-type casing.

[0066] As described above, the blower 100 of embodiment 1 includes: an impeller 1 having a plurality of blades 3; a cylindrical air guide portion 6, the cylindrical air guide portion 6 being configured to cover the outer peripheral ends 3e of the plurality of blades 3; and an annular bell mouth 5. The impeller 1 has a cylindrical hub 2 that is rotationally driven by a motor, and the plurality of blades 3 are radially arranged from the hub 2. Inside the air guide portion 6, air flows from one end of the air guide portion 6 to the other end. The bell mouth 5 is set from a position downstream of one end of the air guide portion 6 and upstream of the impeller 1 to a position upstream of one end of the air guide portion 6. A first suction flow path 7 is formed on the inside of the bell mouth 5, and a second suction flow path 8 is formed on the outside of the bell mouth 5 between the bell mouth 5 and the inner surface of the air guide portion 6. The bell mouth 5 has a minimum radius point Bm in the interval between the upstream end point B0 located at the inlet of the first suction flow path 7 and the downstream end point B1 located at the outlet of the first suction flow path 7, and the radial distance between the minimum radius point Bm and the rotation axis RS of the hub 2 is smaller than the radial distance between the downstream end point B1 and the rotation axis RS of the hub 2.

[0067] Because the minimum radius point Bm exists between the upstream endpoint B0 and the downstream endpoint B1 of the bell mouth 5, the airflow near the downstream endpoint B1 of the bell mouth 5 has a radially outward component, and the airflow flowing in from the second intake flow path 8 flows along the inner surface of the air guide 6. Consequently, compared to conventional systems, the airflow F1 discharged from the second intake flow path 8 can be less likely to interfere with the outer periphery of the blades 3, and the amount of air flowing through the gaps 9 can be increased. Consequently, compared to conventional systems, the leakage flow F2 from the outer peripheral ends 3e of the blades 3 can be suppressed, improving the noise suppression effect and preventing a decrease in air supply performance.

[0068] Furthermore, the inner circumferential surface 51 of the bell mouth 5, which forms the first intake flow path 7, is formed so that, in a cross section along the rotation axis RS, the radial distance between the bell mouth 5 and the rotation axis RS gradually increases from the minimum radius point Bm to the downstream end point B1. This prevents the downstream airflow from separating from the bell mouth 5 near the minimum radius point Bm and guides it.

[0069] Furthermore, the inner peripheral surface 51 is formed into a curved shape, and the outer peripheral surface 52 of the bell mouth 5, which forms the second intake flow path 8 between the bell mouth 5 and the inner surface 61 of the air guide 6, is formed into a curved shape along the inner peripheral surface 51. As a result, the airflow flowing near the downstream end 53 of the bell mouth 5 flows obliquely away from the rotation axis along the curved inner and outer peripheral surfaces 51, 52. Therefore, on the inner peripheral surface 51 side, the airflow discharged from the first intake flow path 7 is less likely to interfere with the wake or blades 3, and on the outer peripheral surface 52 side, the airflow discharged from the second intake flow path 8 is less likely to interfere with the blades 3, thereby further enhancing the noise suppression effect.

[0070] Furthermore, in the bell mouth 5, the outer peripheral surface 52, which forms the second suction flow path 8 between the bell mouth 5 and the inner surface 61 of the air guide 6, is formed so that the radial distance dR from the inner surface 61 of the air guide 6 is constant in the axial direction. This allows for a blower that improves noise suppression by utilizing the curved inner peripheral surface 51 near the downstream end 53 of the bell mouth 5 to mitigate interference between the airflow and the wake or blades 3, without requiring complex processing such as undercutting. This facilitates the manufacture of the bell mouth 5.

[0071] Furthermore, the blower 100 includes a flange portion 12 provided continuously with the upstream end point B0 of the bell mouth 5. The flange portion 12 is configured to separate the upstream side of the inlet of the first suction flow path 7 from the upstream side of the inlet of the second suction flow path 8. This prevents mixing of the airflow at the inlet of the first suction flow path 7 and the inlet of the second suction flow path 8, allows high-pressure airflow to be introduced into the second suction flow path 8, and enhances the effect of suppressing the leakage flow F2 by utilizing airflow at a higher velocity than conventional airflow.

[0072] Implementation method 2.

[0073] Figure 6 This is a partially enlarged schematic diagram of a radial cross-section of a blower 100 according to Embodiment 2. While the relationship between the opening width of the outlet of the second intake flow path 8 and the size of the gap 9 between the outer peripheral end 3e of the blade 3 and the air guide 6 (the tip gap) was not specifically specified in Embodiment 1, the blower 100 according to Embodiment 2 incorporates this requirement to further reduce interference between the airflow and the blades 3. In Embodiment 2, identical components to those in Embodiment 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0074] The casing 4 of the blower 100 of embodiment 2 is constructed so that the radial distance dRs between the downstream end point B1 of the bell mouth 5 and the inner surface 61 of the air guide 6 and the radial distance dRt between the outer peripheral end 3e of the blade 3 and the inner surface 61 of the air guide 6 satisfy the relationship dRt≥dRs.

[0075] In a conventional structure where blades 3 are projected axially so that the outer periphery of blade 3 overlaps the outlet of second intake flow path 8, the width of airflow F1 flowing out of the outlet of second intake flow path 8 becomes wider than the width of leakage flow F2 from the outer peripheral end 3e of blade 3. Consequently, airflow F1 after passing through second intake flow path 8 directly collides with the outer periphery of blade 3, and the airflow is drawn into impeller 1 at an angle different from the pre-set inflow angle. Furthermore, since airflow F1 after passing through second intake flow path 8, which has a faster wind speed than the mainstream, interferes with blade 3, airflow turbulence occurs. Consequently, conventional blowers may not achieve sufficient noise suppression or maintain air supply performance.

[0076] On the other hand, in the blower 100 of Embodiment 2, the radial distance dRs between the downstream end point B1 of the bellmouth 5 and the inner surface 61 of the air guide 6 is approximately equal to or narrower than the tip clearance (distance dRt) formed on the outer circumference of the blades 3. Consequently, the width of the airflow F1 flowing out of the outflow port of the second intake flow path 8 formed between the bellmouth 5 and the air guide 6 is approximately the distance dRs, which is smaller than the tip clearance (distance dRt). This prevents direct interference between the airflow F1 and the blades 3. Consequently, the generation of noise and reduction in airflow performance caused by direct interference between the airflow F1 and the blades 3 can be suppressed.

[0077] Implementation method 3.

[0078] Figure 7 This is a partially enlarged view schematically showing a radial cross section of the blower 100 according to the third embodiment. In the third embodiment, the shape of the downstream end portion 53 including the downstream end point B1 in the bell mouth 5 is the same as that of the first embodiment. Figure 3 In the blower 100 according to the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and their descriptions are omitted.

[0079] The bell mouth 5 of the blower 100 according to Embodiment 3 is formed so that the thickness t1 at the downstream endpoint B1 is thinner than the thickness t0 at the upstream endpoint B0. That is, the thicknesses t0 and t1 of the bell mouth 5 satisfy the relationship t0 > t1. The bell mouth 5 may have a structure in which the thickness gradually changes from the upstream endpoint B0 to the downstream endpoint B1, or it may have a structure in which the thickness changes only at the downstream end 53 of the bell mouth 5, while the thickness remains constant upstream of the downstream end 53.

[0080] However, in order to make the air flow along the bell mouth 5, it is preferred that Figure 7 As shown in FIG, the inner peripheral surface 51 and the outer peripheral surface 52 of the bell mouth 5 are set to be curved. Figure 7In the example shown, the downstream end 53 of the bellmouth 5 is shaped like a triangle with an acute angle at the front end. However, the bellmouth 5 is not particularly limited to this configuration as long as at least the downstream end 53 of the bellmouth 5 tapers at the front end, i.e., the thickness distribution decreases toward the downstream side. The downstream end 53 of the bellmouth 5 may also be shaped, for example, by connecting the inner circumferential surface 51 and the outer circumferential surface 52 with an arc-shaped end surface. In order to minimize the wake region 10 (dead water area) generated downstream of the downstream end point B1 of the bellmouth 5, it is desirable to have the downstream end 53 of the bellmouth 5 be thinner, similar to the trailing edge of a blade (streamlined) shape.

[0081] In the bellmouth 5, where the first suction passage 7 is located on the inner circumferential surface 51 and the second suction passage 8 is located on the outer circumferential surface 52, turbulence of the airflow occurs downstream of the downstream end 53 where the airflows converge, caused by the wake (overflow) and velocity shear layer. The size of the wake region 10 varies depending on the shape of the downstream end 53 of the bellmouth 5. When blades 3 are arranged in the wake region 10, the interference causes turbulence in the airflow, which may cause noise degradation. Therefore, it is preferable to minimize the wake region 10.

[0082] In the bell mouth 5 of the blower 100 of Embodiment 3, the downstream end 53 has a tapered shape. Therefore, compared to conventional bell mouths with uniform thickness and end faces perpendicular to the rotation axis RS, the wake region 10 can be reduced. Furthermore, the turbulence of the airflow caused by the velocity shear layer can be reduced. Consequently, interference between the wake region 10 and the blades 3 can be suppressed, resulting in reduced noise.

[0083] Implementation method 4.

[0084] Figure 8 This is a partially enlarged view schematically showing a radial cross-section of a blower 100 according to Embodiment 4. While the distance between the bellmouth 5 and the blades 3 was not specifically specified in Embodiments 1 to 3, the distance between the bellmouth 5 and the blades 3 is specified in the blower 100 according to Embodiment 4. In the blower 100 according to Embodiment 4, identical components to those in Embodiment 3 are denoted by the same reference numerals, and their descriptions are omitted.

[0085] In embodiment 4, the axial distance H between the downstream end point B1 of the bell mouth 5 and the outer peripheral end point LE1 on the blade leading edge 31 side of the blade 3 is set to be a distance range specified by the lower limit value and upper limit value of the radial distance dRt between the outer peripheral end 3e of the blade 3 and the inner surface 61 of the air guide portion 6.

[0086] If the axial distance H between the downstream end point B1 of the bell mouth 5 and the outer peripheral end point LE1 on the blade leading edge 31 side of the blade 3 is sufficiently smaller than the distance dRt, then Figure 7 As described above, the wake generated downstream of the bell mouth 5 may interfere with the blades 3, thereby worsening the noise. In addition, it is also conceivable that the blades 3 and the bell mouth 5 may come into contact due to deformation or vibration of the impeller 1 during rotation.

[0087] Therefore, in embodiment 4, the bell mouth 5 and the plurality of blades 3 are arranged so that the axial distance H between the downstream end point B1 of the bell mouth 5 and the outer peripheral end point LE1 on the blade leading edge 31 side of the blade 3 is greater than the radial distance dRt between the outer peripheral end 3e of the blade 3 and the inner surface 61 of the air guide portion 6.

[0088] Furthermore, if the axial distance H between the downstream end point B1 of the bell mouth 5 and the outer peripheral end point LE1 on the leading edge 31 side of the blade 3 is sufficiently greater than the distance dRt, the airflow F1 flowing out of the second intake flow path 8 will diffuse in the flow direction until it reaches the vicinity of the outer peripheral end point LE1. Therefore, when the flow velocity of the airflow F1 decreases and reaches the vicinity of the outer peripheral end point LE1 on the leading edge 31 side of the blade 3, the leakage flow F2 will not be sufficiently suppressed.

[0089] Therefore, in Embodiment 4, the bellmouth 5 and the plurality of blades 3 are arranged so that the distance H is smaller than the value obtained by multiplying the distance dRt by 5. In other words, H < 5dRt. By thus setting an upper limit for the distance H, the outer peripheral end point LE1 of the blade 3 can be arranged at a distance where the flow attenuates less, and the airflow F1 flowing out of the second intake flow path 8 can reach the vicinity of the outer peripheral end point LE1 of the blade 3 before diffusing and decelerating. Therefore, the airflow F1 can be effectively used to suppress the leakage flow F2. Here, when the airflow F1 flowing out of the second intake flow path 8 is set as a jet flow, the distance where the flow attenuates less can be pre-set using, for example, the potential core length as a reference.

[0090] Implementation method 5.

[0091] Figure 9 It is a partially enlarged view schematically showing a radial cross section of the air blower according to the fifth embodiment. Figure 10 It will Figure 9Schematic diagram obtained by projecting and unfolding the cylindrical cross section at A-A' of the embodiment. In the blower 100 of embodiment 5, it is different from the cases of embodiments 1 to 4 in that the shell 4 has a plurality of plate-shaped ribs 11. In addition, in the blower 100 of embodiment 5, the relationship between the radial distance dRs between the downstream end point B1 of the bell mouth 5 and the inner surface 61 of the air guide portion 6 and the radial distance dRt between the outer peripheral end 3e of the blade 3 and the inner surface 61 of the air guide portion 6 is dRt<dRs, which is different from the case of embodiment 2. That is, in embodiment 5, it is configured so that when projected along the axial direction of the rotation axis RS, the outer peripheral portion of the blade 3 overlaps with the outflow port of the second suction flow path 8. In addition, in the blower 100 of embodiment 5, the same figure marks are marked on the same structures as in the case of embodiment 3, and the description is omitted.

[0092] exist Figure 10 In the example shown, the trailing edge 32 of each blade 3 is located further back than the leading edge 31 in the direction of rotation of the impeller 1 (direction of arrow R) and further downstream than the leading edge 31. In the blower 100 of embodiment 5, the bell mouth 5 and the air guide 6 ( Figure 9 ) are connected by a plurality of plate-shaped ribs 11. The plurality of ribs 11 are provided in the second suction flow path 8 and are arranged circumferentially. Each rib 11 is arranged circumferentially inclined relative to the upstream-downstream direction (the direction of arrow F), i.e., the axial direction of the rotation axis RS, and functions to change the direction of the airflow F5 passing through the second suction flow path 8.

[0093] exist Figure 10 In the example shown, the ribs 11 are inclined in the same direction as the blades 3. Specifically, the ribs 11 are arranged so that the downstream ends 11b of the ribs 11 are located rearward of the upstream ends 11a in the direction of rotation (direction of arrow R) of the impeller 1. Furthermore, the blades 3 are arranged in the circumferential direction so that the blade leading edges 31 are located between the downstream ends 11b of two adjacent ribs 11.

[0094] Thus, by providing a plurality of ribs 11 in the second suction flow path 8, the direction of the airflow F5 passing through the second suction flow path 8 can be set to any direction in the circumferential direction, and the airflow F1 ( Figure 9 ) flows into the outer periphery of the blade 3 at a desired angle of attack. Therefore, there is no need to set the outflow port of the second suction flow path 8 on the outer periphery of the blade 3 in order to avoid interference between the airflow F1 and the outer periphery of the blade 3 as in the second embodiment. In the blower 100 of the fifth embodiment, by adjusting the airflow F1 from the second suction flow path 8 to be along the direction of the blade 3, the interference between the airflow F1 and the outer periphery of the blade 3 can be suppressed, and the effect of noise suppression can be obtained. In addition, by making the airflow F1 flow into the outer periphery of the blade 3 at a desired angle of attack, the leakage flow F2 ( Figure 9 ), and the inflowing air flow F1 can also be sent out in the axial direction at the outer peripheral portion of the blade 3, thereby improving the air supply performance.

[0095] In addition, the various embodiments may be combined, or the various embodiments may be appropriately modified or omitted. Figure 10 In the example shown, each rib 11 is formed into a flat plate shape, but the shape of the rib 11 is not particularly limited thereto. For example, the rib 11 may have a curved shape such as an arc, and the thickness and shape of the rib 11 may be blade-shaped like a stationary blade.

[0096] The impeller 1 in the blower 100 of Embodiments 1 to 5 is an impeller for an axial flow blower, but the present invention is not limited thereto and an impeller for a diagonal flow blower may also be employed. In this case, for example, the hub 2 is formed into a truncated cone shape and the blades 3 are provided on the outer periphery of the hub 2.

[0097] Description of Reference Numerals

[0098] 1 Impeller, 2 Hub, 3 Blades, 3e Outer Peripheral End, 4 Casing, 5 Bell Mouth, 6 Air Guide, 6a Inlet Side Opening, 6b Discharge Side Opening, 7 First Inlet Flow Path, 8 Second Inlet Flow Path, 9 Gap, 10 Wake Region, 11 Rib, 11a Upstream End, 11b Downstream End, 12 Flange, 31 Blade Leading Edge, 32 Blade Trailing Edge, 51 Inner Peripheral Surface, 52 Outer Peripheral Surface, 53 Downstream End, 61 Inner Surface, 62 Outer Surface, 100 Blower, Ar1 Region, Ar2 Region, Ar3 Region, B0 Upstream End Point, B1 Downstream End Point, Bm Minimum Radius Point, F1, F3, F5, Fi Airflow, Fo1, Fo2 Airflow, H Distance, Ks Noise Ratio, LE1 Outer Peripheral End Point, La Center Line, R1, R1min, dR, dRs, dRt Distances, RS Rotation Axis, U1 Upstream End Point, t, t0, t1 Thickness, φ Flow Coefficient

Claims

1. A blower, wherein: The blower has: an impeller having a cylindrical hub that is rotationally driven by a motor and a plurality of blades radially arranged from the hub; a cylindrical air guide portion, the cylindrical air guide portion being arranged to cover the outer peripheral ends of the plurality of blades and to allow air flow to flow from one end to the other end of the air guide portion; as well as an annular bell mouth, the annular bell mouth being arranged from a position downstream of the one end of the air guide portion and upstream of the impeller to a position upstream of the one end of the air guide portion, forming a first suction flow path on the inner side, and forming a second suction flow path on the outer side between the bell mouth and the inner surface of the air guide portion, The bell mouth has a minimum radius point in a section between an upstream end point located at an inlet of the first suction flow path and a downstream end point located at an outlet of the first suction flow path in the bell mouth, and a radial distance between the minimum radius point and the rotation axis of the hub is smaller than a radial distance between the downstream end point and the rotation axis of the hub. The bell mouth is formed so that a radial distance between the outer peripheral end of the blade and the inner surface of the air guide portion is greater than a radial distance between the downstream end point of the bell mouth and the inner surface of the air guide portion.

2. The blower according to claim 1, wherein: The inner peripheral surface forming the first suction flow path in the bell mouth is formed such that the inner diameter of the bell mouth gradually increases from the minimum radius point to the downstream end point in a cross section passing through the rotation axis.

3. The blower according to claim 2, wherein: The inner peripheral surface is formed in a curved shape, and in the bell mouth, an outer peripheral surface forming the second suction flow path between the bell mouth and the inner surface of the air guide portion is formed in a curved shape along the inner peripheral surface.

4. The blower according to claim 2, wherein: In the bell mouth, an outer peripheral surface forming the second suction flow path with the inner surface of the air guide portion is formed so that a radial distance from the inner surface of the air guide portion is constant in the axial direction.

5. The blower according to any one of claims 1 to 4, wherein: The blower includes a flange portion that is continuously provided to the upstream end point of the bell mouth and separates the upstream side of the inlet of the first suction flow path from the upstream side of the inlet of the second suction flow path.

6. The blower according to any one of claims 1 to 4, wherein: The bell mouth is formed so that a thickness of the bell mouth at the downstream end point is thinner than a thickness of the bell mouth at the upstream end point.

7. The blower according to any one of claims 1 to 4, wherein: The bell mouth and the plurality of blades are arranged such that an axial distance between the downstream end point of the bell mouth and an outer peripheral end point on a leading edge side of the blade is greater than a radial distance between the outer peripheral end of the blade and the inner surface of the air guide portion.

8. The blower according to claim 7, wherein: The bell mouth and the plurality of blades are configured to satisfy the relationship H<5dRt when the axial distance between the downstream end point of the bell mouth and the outer peripheral end point on the leading edge side of the blade is defined as H and the radial distance between the outer peripheral end of the blade and the inner surface of the air guide portion is defined as dRt.

9. The blower according to any one of claims 1 to 4, wherein: The blower includes a plurality of plate-shaped ribs, which are provided in the second suction flow path, connect the bell mouth and the air guide portion, and are arranged in a circumferential direction. The plate-shaped rib is provided obliquely with respect to the axial direction of the rotating shaft, and changes the direction of wind passing through the second suction flow path.

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