centrifugal blower

Abstract

To provide a centrifugal blower which can reduce a pressure loss while reducing a height thereof.SOLUTION: A centrifugal blower 1 includes: an impeller 2 having a disk-like main panel 2a and a plurality of blades 2b installed on a peripheral edge of the main panel 2a, the impeller rotating about a rotational shaft RS that passes through the main panel 2a to generate an air flow; and a scroll casing. The scroll casing includes: a peripheral wall 3a formed in a spiral shape surrounding the impeller 2 from a radial direction of the rotational shaft RS, and having an inner peripheral face facing the impeller 2 and an outer peripheral face opposite to the inner peripheral face; a side wall 3b covering the impeller 2 from an axial direction of the rotational shaft RS and on which an inlet port 5 for taking in an air is formed; a diffuser part formed continuously from a spiral-end part 3e of a spiral shape of the peripheral wall 3a, and arranged such that a cross section of a flow path gradually increases toward an air flow direction; and an outlet port formed of a downstream-side end part of an air flow of the diffuser part and a part of the outer peripheral wall of the peripheral wall 3a, and ejecting the air flow generated by the impeller 2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a centrifugal blower having a scroll casing. [Background technology]

[0002] A conventional centrifugal blower is equipped with an impeller having a disk-shaped main plate and multiple blades attached to the periphery of the main plate, housed within a spiral scroll casing that gradually expands the air passage and leads the air to a discharge port. The scroll casing converts the centrifugal airflow generated by the rotation of the impeller into a unidirectional airflow, increases the pressure, and blows the air out through the discharge port. The discharge port of the scroll casing is formed by a diffuser plate connected to the end of the spiral scroll and an extension plate that faces the diffuser plate and connects to the beginning of the scroll (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6952905 Summary of the Invention [Problem to be solved by the invention]

[0004] When a centrifugal fan is used to supply air into a room, it is installed in a ceiling with the outlet communicating with an opening in the ceiling. In order to install it in a space with limited height, such as above the ceiling, a centrifugal fan with a reduced height when the outlet faces downward is required.

[0005] Furthermore, when the cross-sectional area of ​​the air passage leading to the outlet is large compared to the outlet, as in the case of discharging air directly from the outlet into an indoor space, the airflow discharged from the outlet cannot keep up with the sudden expansion of the air passage shape, resulting in significant pressure loss. Therefore, the outlet must be enlarged to reduce the pressure loss of the airflow at the outlet. The scroll casing is designed so that the cross-sectional area of ​​the air passage from the end of the spiral scroll to the outlet gradually increases, gradually slowing the air velocity and efficiently increasing the static pressure of the airflow. Therefore, to enlarge the outlet, it is necessary to lengthen the distance from the outlet of the spiral scroll to the outlet. However, this creates the problem of increasing the height of the centrifugal fan.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a centrifugal blower that achieves both reduced height and reduced pressure loss when the discharge port is facing downward. [Means for solving the problem]

[0007] The centrifugal fan according to the present disclosure includes an impeller having a disk-shaped main plate and a plurality of blades disposed on the peripheral edge of the main plate, the impeller generating an airflow by rotating about a rotation axis that passes through the center of the main plate and is perpendicular to the main plate, a peripheral wall formed in a spiral shape to surround the impeller from the radial direction of the rotation axis and having an inner peripheral surface facing the impeller and an outer peripheral surface opposite the inner peripheral surface, at least one side wall that covers the impeller from the axial direction of the rotation axis of the impeller and has an inlet port formed therein for taking in air, and a spiral end portion of the peripheral wall. The end of the roll extends from and consecutively Linear when viewed from the direction of the rotation axis The diffuser is formed so that the cross-sectional area of ​​the flow path gradually expands in the direction of the airflow. board and the diffuser board a scroll casing having a discharge port formed by a downstream end of the impeller in the airflow and a part of the outer circumferential surface of the peripheral wall, and through which the airflow generated by the impeller is discharged. A part of the outer peripheral surface of the peripheral wall forming the discharge port includes a discharge port forming point, which is a point on the outer peripheral surface of the peripheral wall closer to the start of the spiral shape of the peripheral wall than the contact point of a tangent to the outer peripheral surface of the peripheral wall that is parallel to the diffuser plate when viewed from the direction of the rotation axis, and the diffuser plate is formed up to a point where the discharge port forming point intersects with the tangent to the scroll casing. . [Effects of the Invention]

[0008] According to the present disclosure, the discharge port is formed by the outer peripheral surface of the peripheral wall of the scroll casing and the diffuser section, so the discharge port can be made larger than if a plate were placed opposite the diffuser section, and a centrifugal blower can be obtained in which the height is kept low when the discharge port is facing downward and pressure loss is reduced. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a centrifugal fan according to a first embodiment. [Figure 2] 1A is a schematic side view showing the internal configuration of a centrifugal blower as seen from the inlet side, and FIG. 1B is a schematic bottom view as seen from the outlet side. [Figure 3] FIG. 2 is a conceptual side view illustrating the shape of a scroll casing. [Figure 4] FIG. 10 is a schematic side view showing the internal configuration of a centrifugal fan according to a second embodiment, as viewed from the inlet side. [Figure 5] FIG. 11 is a schematic side view showing the internal configuration of a centrifugal fan according to a third embodiment, as viewed from the inlet port side. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following description will discuss embodiments of the present disclosure with reference to the accompanying drawings. In each drawing, identical or corresponding parts are designated by the same reference numerals, and redundant descriptions are appropriately simplified or omitted. The present disclosure is not limited to the following embodiments, and any of the components of the embodiments may be modified, combined, or omitted without departing from the spirit of the present disclosure.

[0011] Embodiment 1 Fig. 1 is a perspective view of a centrifugal blower 1 according to a first embodiment of the present disclosure. Note that the portion of scroll casing 3 indicated by the dotted line in Fig. 1 is inside housing 20 and is not visible. Fig. 2 is a schematic side view (a) of the internal configuration of centrifugal blower 1 of Fig. 1 as seen from the suction port 5 side and a schematic bottom view (b) as seen from the discharge port 6 side. The configuration of centrifugal blower 1 of this embodiment will be described using Figs. 1 and 2.

[0012] The centrifugal blower 1 is a multi-blade centrifugal blower such as a sirocco fan or a turbofan. The centrifugal blower 1 includes an impeller 2 that generates an airflow and a scroll casing 3 that houses the impeller 2. The centrifugal blower 1 is disposed in a rectangular parallelepiped housing 20. The housing 20 is formed with an air discharge port 20a that communicates with the discharge port 6 that discharges air from the scroll casing 3. While FIGS. 1 and 2 show an example in which only one centrifugal blower 1 is housed in the housing 20, the centrifugal blower 1 of the present disclosure can also be applied to an intake / exhaust type ventilation fan that includes multiple centrifugal blowers, or to an air conditioner that includes a centrifugal blower and a heat exchanger.

[0013] The impeller 2 is driven to rotate about a rotation axis RS by a motor (not shown), and centrifugal force generated by the rotation forcibly sends air outward in the radial direction. As shown in FIG. 1, the impeller 2 has a disk-shaped main plate 2a and multiple blades 2b attached to the peripheral edge of the main plate 2a. A shaft 2c is provided at the center of the main plate 2a. A motor is connected to the center of the shaft 2c, and the impeller 2 rotates by the driving force of the motor around a rotation axis RS that passes through the center of the shaft 2c and is perpendicular to the main plate 2a. The impeller 2 also has a ring-shaped side plate (not shown) facing the main plate 2a at the end of the multiple blades 2b opposite the main plate 2a in the axial direction of the rotation axis RS of the shaft 2c. The side plate connects the multiple blades 2b, maintaining the positional relationship between the tips of the blades 2b and reinforcing the multiple blades 2b. Note that the impeller 2 may have a structure without a side plate. When the impeller 2 has a side plate, one end of each of the multiple blades 2b is connected to the main plate 2a and the other end is connected to the side plate, and the multiple blades 2b are arranged between the main plate 2a and the side plate. The impeller 2 is configured in a cylindrical shape by the main plate 2a and the multiple blades 2b, and the side opposite to the main plate 2a in the axial direction of the rotation axis RS of the shaft portion 2c is open, and the open portion communicates with the suction port 5 of the scroll casing 3 for sucking air into the impeller 2.

[0014] The impeller 2 has the above-described configuration, and when rotated around the rotation axis RS, it can suck air into the space surrounded by the main plate 2a and the plurality of blades 2b and send it out radially outward through the spaces between the blades 2b and adjacent blades 2b.

[0015] As shown in FIG. 1, the scroll casing 3 houses the impeller 2. The scroll casing 3 rectifies the air blown out from the impeller 2. The scroll casing 3 has a scroll section 3g and a discharge section 3h. The discharge section 3h forms a discharge port 6 through which the airflow generated by the impeller 2 and passing through the scroll section 3g is discharged. The scroll section 3g forms an air passage that converts the dynamic pressure of the airflow generated by the impeller 2 into static pressure. The scroll section 3g covers the impeller 2 in the axial direction of the rotation axis RS of the shaft section 2c constituting the impeller 2 and has a sidewall 3b with an inlet 5 for taking in air, a sidewall 3b' facing the sidewall 3b, and a peripheral wall 3a that surrounds the impeller 2 in the radial direction of the rotation axis RS of the shaft section 2c. The radial direction of the shaft section 2c is the direction perpendicular to the rotation axis RS of the shaft section 2c. The internal space of the scroll portion 3g, which is formed by the peripheral wall 3a and the side wall 3b, is a space in which the air blown out from the impeller 2 flows along the peripheral wall 3a.

[0016] The side wall 3b is disposed perpendicular to the axial direction of the rotation axis RS of the impeller 2 and covers the impeller 2. An intake port 5 is formed in the side wall 3b of the scroll casing 3 to allow air to circulate between the impeller 2 and the outside of the scroll casing 3. The side wall 3b is also provided with a bell mouth 7 that guides the airflow drawn into the scroll casing 3 through the intake port 5. The bell mouth 7 is formed in an annular shape, with the opening diameter gradually narrowing from the upstream side to the downstream side of the airflow drawn into the scroll casing 3 through the intake port 5. The intake port 5 is formed in a circular shape and is disposed so that the center of the intake port 5 and the center of the shaft portion 2c of the impeller 2 approximately coincide with each other. Air near the intake port 5 flows smoothly along the bell mouth 7 and efficiently flows from the intake port 5 into the impeller 2. The configuration and form of the bell mouth 7 are not particularly limited. FIG. 1 shows a single-suction type centrifugal blower 1. A single-suction type centrifugal blower 1 is required to have at least one side wall 3b with an inlet 5. That is, in a single-suction type centrifugal blower 1, the scroll casing 3 has one side wall 3b with an inlet 5 and one side wall 3b' without an inlet 5, and the side walls 3b and 3b' are arranged to face each other. Hereinafter, the side wall 3b with an inlet 5 will be referred to as the side surface.

[0017] The peripheral wall 3a surrounds the impeller 2 in the radial direction of the shaft portion 2c and forms an inner peripheral surface facing the multiple blades 2b that form the radially outer peripheral side of the impeller 2. The peripheral wall 3a is disposed parallel to the axial direction of the rotation shaft RS of the impeller 2 and covers the impeller 2. As shown in FIG. 2(a), the peripheral wall 3a is provided in a section from the winding start portion 3d to the winding end portion 3e that is located at the boundary between the discharge portion 3h and the scroll portion 3g along the rotation direction of the impeller 2. The winding start portion 3d is the upstream edge of the curved surface of the peripheral wall 3a in the airflow generated by the rotation of the impeller 2, and the winding end portion 3e is the downstream edge of the airflow generated by the rotation of the impeller 2.

[0018] The peripheral wall 3a has a width in the axial direction of the rotation axis RS of the impeller 2. As shown in FIG. 2(a), the peripheral wall 3a is formed in a spiral shape defined by a predetermined expansion rate, in which the distance from the rotation axis RS defined by the shaft portion 2c gradually increases in the rotation direction of the impeller 2 (the direction of arrow R). In other words, from the start portion 3d to the end portion 3e of the spiral, the gap between the peripheral wall 3a and the outer periphery of the impeller 2 expands at a constant rate, and the air flow path area gradually increases. Examples of spiral shapes defined by a constant expansion rate include a logarithmic spiral, an Archimedean spiral, or a spiral shape based on an involute curve. The inner peripheral surface of the peripheral wall 3a facing the impeller 2 forms a curved surface that smoothly curves along the circumferential direction of the impeller 2 from the start portion 3d, where the spiral shape begins, to the end portion 3e, where the spiral shape ends. With this configuration, the air sent out from the impeller 2 flows smoothly through the gap between the impeller 2 and the peripheral wall 3a in the direction of arrow F in Figure 2(a). As a result, inside the scroll casing 3, the static pressure of the air increases efficiently toward the discharge section 3h.

[0019] The discharge section 3h has a discharge port 6 through which air that has passed through the scroll section 3g is discharged to the outside of the scroll casing 3. The discharge port 6 is an opening on the downstream side of the discharge section 3h. The discharge section 3h is an air passage formed by the diffuser plate 3c, the outer peripheral surface of the peripheral wall 3a facing the diffuser plate 3c from the winding start portion 3d to the discharge port forming point 4, a portion of the side wall 3b, and a portion of the side wall 3b' facing the side wall 3b. The discharge port forming point 4 is an arbitrary point on the outer peripheral surface of the peripheral wall 3a. The discharge port 6 is formed by the downstream end of the diffuser plate 3c in the airflow, a line parallel to the rotation axis RS that includes the discharge port forming point 4 on the outer peripheral surface of the peripheral wall 3a, and the downstream ends of the side wall 3b and side wall 3b' in the airflow. The diffuser plate 3c is formed continuously with the winding end portion 3e of the scroll section 3g so as to extend from the winding end portion 3e. The diffuser plate 3c is a diffuser portion in the scroll casing 3 that guides air discharged from the scroll section 3g to the discharge port 6. In this embodiment, the diffuser portion is plate-shaped, so it is referred to as the diffuser plate 3c. However, the diffuser portion is not limited to a plate-shaped diffuser plate as long as it has a surface that extends from the end of the scroll section 3g to the discharge port 6. As shown in FIG. 2(a), the diffuser plate 3c is arranged so that it widens toward the discharge port as viewed from the suction port 5 relative to the outer peripheral surface of the peripheral wall 3a facing the diffuser plate 3c, from the beginning of the scroll section 3d to the discharge port-forming point 4. With this configuration, the cross-sectional area of ​​the air passage of the discharge section 3h gradually expands from upstream to downstream, gradually slowing the air velocity of the air passing through the discharge section 3h and increasing the static pressure. By forming the surface of the discharge section 3h on the outer peripheral surface of the peripheral wall 3a of the scroll casing 3, the expansion rate of the discharge section 3h is greater than if a plate were arranged facing the diffuser plate 3c, and the discharge port 6 can be made larger.

[0020] FIG. 3 is a schematic side view illustrating the shape of the scroll casing 3. The shape of the diffuser plate 3c will be described using FIG. 3. The diffuser plate 3c is formed so as to extend continuously from the end-of-volute portion 3e of the peripheral wall 3a. The length of the diffuser plate 3c from the end-of-volute portion 3e to the end forming the discharge port 6 is the length from the end-of-volute portion 3e to point G, where line L1, which overlaps with the diffuser plate 3c extended from the end-of-volute portion 3e, intersects with tangent line T to the scroll portion 3g at the discharge port forming point 4. As a result, when the discharge port forming point 4 is the lower end as viewed from the side, the discharge port 6 faces downward. It is known that the air flowing through the scroll casing 3 is sufficiently pressurized by setting the angle A between the line S connecting the center of the shaft portion 2c and the start-of-volute portion 3d and the line L2, which passes through the center of the shaft portion 2c and is parallel to the diffuser plate 3c, to be 0 degrees or greater.

[0021] Next, a method for determining discharge port defining point 4 will be explained using Figure 3. A point on the outer peripheral surface of peripheral wall 3a that is closer to winding-start portion 3d than point of contact F of tangent line L3 to the outer peripheral surface of peripheral wall 3a, which is parallel to line L1, is determined to be discharge port defining point 4. As a result, point G exists where line L1 and tangent line T to scroll portion 3g at discharge port defining point 4 intersect.

[0022] By configuring the discharge port forming point 4 and the diffuser plate 3c as described above, the height of the scroll casing 3 when the discharge port 6 faces downward is the distance H between the tangent line T at the discharge port forming point 4 and a line T2 that passes through the upper end of the scroll section 3g and is parallel to the tangent line T. Therefore, the height of the scroll casing 3 when the discharge port 6 faces downward is determined by the size of the scroll section 3g.

[0023] As shown in FIGS. 2( a) and 2(b), the casing 20 is box-shaped and has a surface on which a discharge port 20a communicating with the discharge port 6 of the scroll casing 3 is formed. The inner wall of the surface on which the discharge port 20a of the casing 20 is formed is in close contact with a line parallel to the rotation axis RS including the discharge port forming point 4 on the outer peripheral surface of the peripheral wall 3a. With this configuration, air discharged from the discharge port 6 of the scroll casing 3 does not enter the interior of the casing 20 but is discharged from the discharge port 20a of the casing 20. Note that the outer peripheral surface of the peripheral wall 3a that is in close contact with the inner wall of the surface on which the discharge port 20a of the casing 20 is formed does not have to be in close contact with a line parallel to the rotation axis RS including the discharge port forming point 4, as long as it is the outer peripheral surface of the peripheral wall 3a, it is possible to prevent the air discharged from the discharge port 6 of the scroll casing 3 from entering the interior of the casing 20.

[0024] Next, the operation of the centrifugal blower 1 will be described. Air outside the scroll casing 3 is drawn into the scroll casing 3 through the suction port 5. The air drawn into the scroll casing 3 is guided by the bell mouth 7 and drawn into the impeller 2. As the air drawn into the impeller 2 passes between the blades 2b, it becomes an airflow to which dynamic and static pressures are added, and is then blown out radially outward from the impeller 2. The airflow blown out from the impeller 2 is rectified while being guided between the inside of the peripheral wall 3a and the blades 2b in the scroll section 3g, and the dynamic pressure is converted into static pressure. After passing through the scroll section 3g, the airflow blown out from the impeller 2 is blown out of the scroll casing 3 through the discharge port 6 formed in the discharge section 3h.

[0025] The air discharged from the discharge port 6 to the outside of the scroll casing 3 flows into a duct (not shown) connected to the discharge port 6. If the cross-sectional area of ​​the duct connected to the discharge port 6 is large compared to the discharge port 6, the airflow cannot keep up with the sudden expansion of the air path, resulting in pressure loss. Alternatively, even when no duct is connected to the discharge port 6 and the air is discharged from the discharge port 6 into a space such as a room, the airflow cannot keep up with the sudden expansion of the air path, resulting in pressure loss. In the centrifugal blower 1 of the present disclosure, the surface constituting the discharge section 3h is the outer peripheral surface of the peripheral wall 3a of the scroll casing 3, which increases the expansion rate of the discharge section 3h compared to when a plate is placed opposite the diffuser plate 3c, thereby enabling the discharge port 6 to be larger. This reduces pressure loss at the discharge port 6. Furthermore, reducing pressure loss reduces power consumption relative to the amount of air discharged from the discharge port 6, resulting in a highly efficient centrifugal blower 1.

[0026] As described above, the centrifugal fan 1 in this embodiment includes the impeller 2 having a disk-shaped main plate 2a and a plurality of blades 2b installed on the peripheral edge of the main plate 2a, which generates an airflow by rotating about a rotation axis RS that passes through the center of the main plate 2a and is perpendicular to the main plate 2a, the peripheral wall 3a formed in a spiral shape so as to surround the impeller 2 in the radial direction of the rotation axis RS, and having an inner circumferential surface facing the impeller 2 and an outer circumferential surface that is the surface opposite the inner circumferential surface, and the impeller 2 extending in the axial direction of the rotation axis RS. The scroll casing 3 has at least one side wall 3b that covers the impeller 2 and has an inlet 5 formed therein for taking in air, a diffuser section that is formed continuously with the spiral-shaped end portion 3e of the peripheral wall 3a and is arranged so that the cross-sectional area of ​​the flow path gradually increases in the direction of the airflow, and a discharge port 6 that is formed by the downstream end of the diffuser section in the airflow and a part of the outer circumferential surface of the peripheral wall 3a and discharges the airflow generated by the impeller 2.

[0027] With this configuration, the discharge port 6 is formed by the downstream end of the diffuser plate 3c in the airflow and a part of the outer circumferential surface of the peripheral wall 3a, and thus the height of the discharge port 6 of the scroll casing 3 facing downward can be kept equal to the width of the scroll section 3g, while the discharge port 6 can be made larger, compared to arranging a plate facing the diffuser plate 3c. This reduces pressure loss at the discharge port 6, and makes it possible to obtain a highly efficient centrifugal blower 1.

[0028] The centrifugal blower 1 further includes a housing 20 that has an opening (discharge port 20a) on one surface that communicates with the discharge port 6 and that houses the scroll casing 3, and a part of the outer peripheral surface of the peripheral wall 3a is in close contact with the inner wall of the housing 20 on one surface that has the opening. With this configuration, the air discharged from the discharge port 6 does not enter the inside of the housing 20, but is discharged from the discharge port 20a of the housing 20.

[0029] The centrifugal blower 1 has been described as a double-suction type centrifugal blower. In this embodiment, the centrifugal blower 1 may also be a double-suction type centrifugal blower 1. A double-suction type centrifugal blower 1 has a scroll casing 3 having side walls 3b with suction ports 5 formed on both sides of the main plate 2a in the axial direction of the rotation axis RS of the shaft portion 2c. That is, in a double-suction type centrifugal blower 1, the scroll casing 3 has two side walls 3b with suction ports 5 formed on each side, and the two side walls 3b are arranged to face each other.

[0030] Embodiment 2 Next, a second embodiment will be described with reference to Fig. 4. Fig. 4 is a schematic side view showing the internal configuration of centrifugal blower 1 according to the second embodiment as viewed from the suction port 5 side. Note that, in this embodiment, descriptions of parts that are the same as those in the above-described embodiments will be omitted.

[0031] As shown in FIG. 4, the centrifugal blower 1 of this embodiment includes an arc-shaped tongue portion 3f on the peripheral wall 3a of the scroll casing 3, which has a constant radius of curvature from the spiral start portion 3d, where the spiral shape begins, toward the outer periphery. When the airflow generated by the rotation of the impeller 2 and rectified by the scroll portion 3g flows from the scroll portion 3g to the discharge portion 3h, the tongue portion 3f serves as a branching point for the flow path. That is, air flowing near the end portion 3e of the scroll portion 3g strikes the tongue portion 3f and branches into air that flows into the discharge portion 3h and air that flows into the interior of the peripheral wall 3a and passes through the scroll portion 3g again. The static pressure of the air flowing into the discharge portion 3h increases as it passes through the scroll casing 3, making it higher than the pressure inside the scroll portion 3g. Therefore, the tongue portion 3f not only serves to resolve this pressure difference but also, through its curved surface, serves to guide the air flowing into the discharge portion 3h to each flow path. By having an appropriate radius of curvature for the tongue portion 3f, the air that hits the tongue portion 3f flows smoothly into the discharge portion 3h or the scroll portion 3g, thereby reducing noise. The appropriate radius of curvature for the tongue portion 3f varies depending on the air volume of the impeller 2 and the size of the scroll casing.

[0032] Even if the material of the peripheral wall 3a of the scroll casing 3 is thinner than the appropriate diameter of the curvature circle of the tongue portion 3f, the thickness of the peripheral wall 3a of the scroll casing 3 gradually increases from the discharge port forming point 4 to the winding start point 3d, as shown in FIG. 4, to form a tongue portion 3f with a constant radius of curvature. That is, twice the radius of curvature of the tongue portion 3f is greater than the thickness of the peripheral wall 3a, forming an arc with an appropriate radius of curvature. The thickness of the peripheral wall 3a is the distance from a point on the outer surface of the peripheral wall 3a to the inner surface of a line drawn perpendicular to the tangent to the outer surface at that point. In particular, in this embodiment, the thickness of the peripheral wall 3a refers to the distance from a point on the outer surface of the peripheral wall 3a from the winding end point 3e to the discharge port forming point 4 to the inner surface of a line drawn perpendicular to the tangent to the outer surface at that point. This configuration enables the scroll casing 3 to be both lightweight and quiet.

[0033] As described above, the centrifugal fan 1 in this embodiment includes the impeller 2 having a disk-shaped main plate 2a and a plurality of blades 2b installed on the peripheral edge of the main plate 2a, which generates an airflow by rotating about a rotation axis RS that passes through the center of the main plate 2a and is perpendicular to the main plate 2a, the peripheral wall 3a formed in a spiral shape so as to surround the impeller 2 in the radial direction of the rotation axis RS and having an inner circumferential surface facing the impeller 2 and an outer circumferential surface that is the surface opposite to the inner circumferential surface, and at least one side wall 3b that covers the impeller 2 in the axial direction of the rotation axis RS of the impeller 2 and has an inlet 5 that takes in air. a scroll casing 3 having a spiral casing 3b, a diffuser section formed continuously with the spiral end section 3e of the peripheral wall 3a and arranged so that the cross-sectional area of ​​the flow path gradually increases in the direction of the airflow, and a discharge port 6 formed by the downstream end of the diffuser section in the airflow and a part of the outer peripheral surface of the peripheral wall 3a, for discharging the airflow generated by the impeller 2, wherein the peripheral wall 3a further has an arc-shaped tongue section 3f extending from the spiral start section 3d toward the outer peripheral surface, and twice the radius of curvature of the tongue section 3f is greater than the thickness of the peripheral wall 3a.

[0034] With this configuration, air flowing near the end of scroll section 3e of scroll section 3g hits tongue section 3f and is smoothly branched into air that flows into discharge section 3h and air that flows into the interior of peripheral wall 3a and passes through scroll section 3g again, thereby suppressing noise. Furthermore, even if the peripheral wall 3a of scroll casing 3 is made of a material thinner than the appropriate diameter of the circle of curvature of tongue section 3f, tongue section 3f can be formed with a constant radius of curvature, allowing for both weight reduction and noise reduction of scroll casing 3.

[0035] The peripheral wall 3a is also characterized in that its thickness gradually increases from a portion of the outer circumferential surface toward the winding start portion 3d. With this configuration, even if the peripheral wall 3a of the scroll casing 3 is made of a material thinner than the appropriate diameter of the circle of curvature of the tongue portion 3f, it is possible to form the tongue portion 3f with a constant radius of curvature, thereby achieving both a reduction in weight and noise of the scroll casing 3.

[0036] Embodiment 3 Next, a third embodiment will be described with reference to Fig. 5. Fig. 5 is a schematic side view showing the internal configuration of centrifugal blower 1 according to the third embodiment as viewed from the suction port 5 side. Note that, in this embodiment, descriptions of parts that are the same as those in the above-described embodiments will be omitted.

[0037] As shown in FIG. 5 , in the centrifugal blower 1 of this embodiment, the peripheral wall 3a of the scroll casing 3 curves from a spiral start portion 3d, where the spiral shape begins, toward the outer circumferential surface. The curved surface of the peripheral wall 3a curving from the spiral start portion 3d toward the outer circumferential surface forms an arc-shaped tongue portion 3f with a constant radius of curvature. By curving the peripheral wall 3a of the scroll casing 3 from the spiral start portion 3d toward the outer circumferential surface, the tongue portion 3f can be formed with a constant radius of curvature even when the peripheral wall of the scroll casing 3 is made of a material thinner than the appropriate diameter of the circle of curvature of the tongue portion 3f. Therefore, because the tongue portion 3f has an appropriate radius of curvature, air that hits the tongue portion 3f flows smoothly into the discharge portion 3h or the scroll portion 3g, thereby reducing noise.

[0038] As described above, the centrifugal fan 1 in this embodiment includes the impeller 2 having a disk-shaped main plate 2a and a plurality of blades 2b installed on the peripheral edge of the main plate 2a, which generates an airflow by rotating about a rotation axis RS that passes through the center of the main plate 2a and is perpendicular to the main plate 2a, the peripheral wall 3a formed in a spiral shape so as to surround the impeller 2 in the radial direction of the rotation axis RS and having an inner circumferential surface facing the impeller 2 and an outer circumferential surface that is the surface opposite to the inner circumferential surface, at least one side wall 3b that covers the impeller 2 in the axial direction of the rotation axis RS of the impeller 2 and has an inlet 5 that takes in air, and the spiral end of the peripheral wall 3a and a scroll casing (3) having a diffuser section formed continuously with the first section (3e) and arranged so that the cross-sectional area of ​​the flow path gradually increases in the direction of the airflow, and a discharge port (6) formed by the downstream end of the diffuser section in the airflow and a part of the outer peripheral surface of the peripheral wall (3a), through which the airflow generated by the impeller (2) is discharged. The peripheral wall (3a) further has an arc-shaped tongue section (3f) extending from the spiral-shaped start section (3d) toward the outer peripheral surface, and twice the radius of curvature of the tongue section (3f) is greater than the thickness of the peripheral wall (3a), and the tongue section (3f) is a curved surface where the peripheral wall (3a) curves from the start section (3d) toward the outer peripheral surface of the peripheral wall (3a).

[0039] With this configuration, even if the peripheral wall 3a of the scroll casing 3 is made of a material thinner than the appropriate diameter of the curvature circle of the tongue portion 3f, it is possible to form a tongue portion 3f having a constant radius of curvature, thereby achieving both weight reduction and noise reduction of the scroll casing 3.

[0040] The configurations shown in the above embodiments are examples of the content of the present invention, and may be combined with other known technologies, and parts of the configurations may be omitted or modified within the scope of the gist of the present invention.

[0041] Examples of aspects that may be included in the present disclosure are set forth below as appendices. (Appendix 1) an impeller having a disk-shaped main plate and a plurality of blades installed on the peripheral edge of the main plate, the impeller rotating about a rotation axis that passes through the center of the main plate and is perpendicular to the main plate to generate an airflow; a scroll casing including: a peripheral wall formed in a spiral shape so as to surround the impeller from the radial direction of the rotary shaft, the peripheral wall having an inner peripheral surface facing the impeller and an outer peripheral surface opposite the inner peripheral surface; at least one side wall covering the impeller from the axial direction of the rotary shaft of the impeller and having an inlet port formed therein for taking in air; a diffuser section formed continuously with the spiral end portion of the peripheral wall and arranged so that the cross-sectional area of ​​the flow path gradually increases in the direction of the airflow; and a discharge port formed by the downstream end of the diffuser section in the airflow and a part of the outer peripheral surface of the peripheral wall, for discharging the airflow generated by the impeller; A centrifugal blower equipped with (Appendix 2) an opening communicating with the discharge port is formed on one surface of the housing for accommodating the scroll casing; 2. The centrifugal blower according to claim 1, wherein a portion of the outer peripheral surface of the peripheral wall is in close contact with the inner wall of the one surface of the housing having the opening. (Appendix 3) The peripheral wall has an arc-shaped tongue portion extending from a spiral start portion toward the outer circumferential surface, 3. The centrifugal blower according to claim 1, wherein twice the radius of curvature of the tongue portion is greater than the thickness of the peripheral wall. (Appendix 4) 4. The centrifugal blower according to claim 3, wherein the thickness of the peripheral wall gradually increases from a portion of the outer circumferential surface toward the winding start portion. (Appendix 5) The centrifugal blower according to Supplementary Note 3, wherein the tongue portion is a curved surface in which the peripheral wall curves from the winding start portion toward the outer circumferential surface. [Explanation of symbols]

[0042] 1 centrifugal blower, 2 impeller, 2a main plate, 2b blade, 2c shaft, 3 scroll casing, 3a peripheral wall, 3b side wall, 3c diffuser plate, 3d start of winding, 3e end of winding, 3f tongue, 3g scroll, 3h discharge, 4 discharge port configuration point, 5 suction port, 6 discharge port, 7 bell mouth, 20 housing, 20a discharge port, RS rotating shaft.

Claims

1. an impeller having a disk-shaped main plate and a plurality of blades installed on the peripheral edge of the main plate, the impeller rotating about a rotation axis that passes through the center of the main plate and is perpendicular to the main plate to generate an airflow; a scroll casing including: a peripheral wall formed in a spiral shape so as to surround the impeller from the radial direction of the rotation shaft, the peripheral wall having an inner peripheral surface facing the impeller and an outer peripheral surface opposite the inner peripheral surface; at least one side wall covering the impeller from the axial direction of the rotation shaft of the impeller and having an inlet port formed therein for taking in air; a diffuser plate extending from an end portion of the spiral shape of the peripheral wall, continuous with the end portion, and formed linearly when viewed from the rotation axis direction, the diffuser plate being disposed so that the cross-sectional area of ​​its flow path gradually increases in the direction of the airflow; and a discharge port formed by an end portion of the diffuser plate on a downstream side in the airflow and a part of the outer peripheral surface of the peripheral wall, for discharging the airflow generated by the impeller; Equipped with a part of the outer peripheral surface of the peripheral wall that forms the discharge port includes a discharge port forming point, which is a point on the outer peripheral surface of the peripheral wall that is closer to a start point of a spiral shape of the peripheral wall than a contact point of a tangent to the outer peripheral surface of the peripheral wall that is parallel to the diffuser plate, as viewed from the rotation axis direction, The diffuser plate is formed to have a length extending to a point where the diffuser plate intersects with a tangent line of the scroll casing at the discharge port defining point.

2. an opening communicating with the discharge port is formed on one surface of the housing for accommodating the scroll casing; 2. The centrifugal blower according to claim 1, wherein a part of the outer peripheral surface of the peripheral wall is in close contact with the inner wall of the one surface of the housing having the opening.

3. The peripheral wall has an arc-shaped tongue portion extending from a spiral start portion toward the outer circumferential surface, 3. The centrifugal blower according to claim 1, wherein twice the radius of curvature of the tongue portion is greater than the thickness of the peripheral wall.

4. 4. The centrifugal blower according to claim 3, wherein the thickness of the peripheral wall gradually increases from a portion of the outer circumferential surface toward the winding start portion.

5. 4. The centrifugal blower according to claim 3, wherein the tongue portion is a curved surface in which the peripheral wall curves from the winding start portion toward the outer circumferential surface.

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