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 installed on the periphery of the main plate, inside a spiral scroll casing that gradually expands the air passage and leads it 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 it out from the discharge port. In addition, the discharge port of the scroll casing is formed by a diffuser plate connected to the end of the scroll of the spiral shape, and an extension plate that faces the diffuser plate and connects to the start of the scroll (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 embedded in the ceiling and installed so that the outlet communicates with an opening in the ceiling. In order to install the fan 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] In addition, when the cross-sectional area of ​​the air passage leading to the discharge port is large compared to the discharge port, such as when air is discharged directly from the discharge port into an indoor space, the airflow discharged from the discharge port cannot keep up with the sudden expansion of the air passage shape, resulting in a large pressure loss. Therefore, it is necessary to enlarge the discharge port in order to reduce the pressure loss of the airflow at the discharge port. The scroll casing is formed so that the cross-sectional area of ​​the air passage from the end of the spiral scroll to the discharge port gradually increases, gradually slowing down the wind speed and efficiently increasing the static pressure of the airflow. Therefore, in order to enlarge the discharge port, it is necessary to lengthen the distance from the outlet of the spiral scroll to the discharge port. However, this creates the problem of increasing the height of the centrifugal blower.

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

[0007] The centrifugal blower according to the present disclosure comprises: an impeller having a disk-shaped main plate and a plurality of blades mounted on the peripheral edge of the main plate and 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 so as to surround the impeller in the radial direction of the rotation axis and having an inner circumferential surface facing the impeller and an outer circumferential surface that is the surface opposite the inner circumferential surface; at least one side wall that covers the impeller in the axial direction of the rotation axis of the impeller and has an intake 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 airflow in the diffuser section and a part of the outer circumferential surface of the peripheral wall and for discharging the airflow generated by the impeller. Effect 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 that the discharge port can be made larger than by placing a plate facing the diffuser section, and it is possible to obtain a centrifugal blower in which the height is kept small when the discharge port is facing downward and pressure loss is reduced. [Brief description of the drawings]

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

[0010] The embodiments for carrying out the subject of the present disclosure will be described with reference to the accompanying drawings. In each drawing, the same or corresponding parts are given the same reference numerals, and duplicated descriptions are appropriately simplified or omitted. Note that the subject of the present disclosure is not limited to the following embodiments, and any of the components of the embodiments may be modified, combined, or omitted within the scope of the gist 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 the scroll casing 3 indicated by the dotted line in Fig. 1 is inside the housing 20 and is not visible. Fig. 2 is a schematic side view (a) showing the internal configuration of the centrifugal blower 1 in Fig. 1 as viewed from the suction port 5 side, and a schematic bottom view (b) as viewed from the discharge port 6 side. The configuration of the centrifugal blower 1 of this embodiment will be described with reference to Figs. 1 and 2.

[0012] The centrifugal blower 1 is, for example, a multi-blade centrifugal type centrifugal blower such as a sirocco fan or a turbo fan. 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 outlet 20a that communicates with an outlet 6 that discharges air from the scroll casing 3. Although 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 exhaust ventilation fan that includes multiple centrifugal blowers, or an air conditioner that includes a centrifugal blower and a heat exchanger.

[0013] The impeller 2 is driven to rotate around a rotation axis RS by a motor (not shown), and the 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 a plurality of blades 2b installed on the periphery of the main plate 2a. A shaft portion 2c is provided at the center of the main plate 2a. A motor is connected to the center of the shaft portion 2c, and the impeller 2 rotates around a rotation axis RS that passes through the center of the shaft portion 2c and is perpendicular to the main plate 2a by the driving force of the motor. The impeller 2 also has a ring-shaped side plate (not shown) that faces the main plate 2a at the end of the plurality of blades 2b opposite the main plate 2a in the axial direction of the rotation axis RS of the shaft portion 2c. The side plate connects the plurality of blades 2b to each other, thereby maintaining the positional relationship of the tips of the blades 2b and reinforcing the plurality of blades 2b. The impeller 2 may have a structure that does not include a side plate. When the impeller 2 has a side plate, each of the multiple blades 2b has one end connected to the main plate 2a and the other end 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 in air into the space surrounded by the main plate 2a and the multiple blades 2b and send it radially outward through the spaces between the blades 2b and the adjacent blades 2b.

[0015] The scroll casing 3 houses the impeller 2 therein as shown in FIG. 1. The scroll casing 3 straightens 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 from the axial direction of the rotation axis RS of the shaft section 2c constituting the impeller 2, and has a side wall 3b in which an inlet 5 for taking in air is formed, a side wall 3b' facing the side wall 3b, and a peripheral wall 3a that surrounds the impeller 2 from the radial direction of the rotation axis RS of the shaft section 2c. The radial direction of the shaft section 2c is a 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 through 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. The side wall 3b of the scroll casing 3 is formed with an intake port 5 so that air can flow 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 sucked into the scroll casing 3 through the intake port 5. The bell mouth 7 is formed in an annular shape whose opening diameter gradually narrows from the upstream side to the downstream side of the airflow sucked 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 are approximately aligned. The air near the intake port 5 flows smoothly along the bell mouth 7 and efficiently flows into the impeller 2 from the intake port 5. The configuration and form of the bell mouth 7 are not particularly limited. FIG. 1 shows a centrifugal blower 1 of a single intake type. A single-suction type centrifugal blower 1 may have at least one side wall 3b with a suction port 5 formed therein. That is, in a single-suction type centrifugal blower 1, the scroll casing 3 has one side wall 3b with a suction port 5 formed therein and one side wall 3b' without a suction port 5 formed therein, and the side walls 3b and 3b' are disposed so as to face each other. In the following description, the side wall 3b with the suction port 5 formed therein will be referred to as a side surface.

[0017] The peripheral wall 3a surrounds the impeller 2 from the radial direction of the shaft portion 2c and constitutes an inner peripheral surface facing the multiple blades 2b that constitute the radial outer peripheral side of the impeller 2. The peripheral wall 3a is arranged 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 portion from the winding start portion 3d to the winding end portion 3e 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 an edge portion on the upstream side of the airflow generated by the rotation of the impeller 2 in the peripheral wall 3a that constitutes a curved surface, and the winding end portion 3e is an edge portion on the downstream side 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 ratio in which the distance from the rotation axis RS formed by the shaft portion 2c gradually increases as the rotation direction (arrow R direction) of the impeller 2 progresses. In other words, the gap between the peripheral wall 3a and the outer periphery of the impeller 2 expands at a constant rate from the start of the spiral 3d to the end of the spiral 3e, and the air flow passage area gradually increases. Examples of the spiral shape defined by a constant expansion ratio 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 of the spiral 3d, which is the start of the spiral shape, to the end of the spiral 3e, which is the end of the spiral shape. 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 the arrow F in Fig. 2(a). Therefore, inside the scroll casing 3, the static pressure of the air increases efficiently toward the discharge section 3h.

[0019] The discharge section 3h is formed with 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 from the start of the winding 3d facing the diffuser plate 3c to the discharge port configuration point 4, a part of the side wall 3b, and a part of the side wall 3b' facing the side wall 3b. The discharge port configuration 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 airflow of the diffuser plate 3c, a line parallel to the rotation axis RS including the discharge port configuration point 4 on the outer peripheral surface of the peripheral wall 3a, and the downstream ends of the airflow of the side wall 3b and the side wall 3b'. The diffuser plate 3c is formed continuously with the end of the winding 3e of the scroll section 3g so as to extend from the end of the winding 3e. The diffuser plate 3c is a diffuser portion that guides the air discharged from the scroll portion 3g in the scroll casing 3 to the discharge port 6. In this embodiment, the diffuser portion is plate-shaped, so it is called the diffuser plate 3c, but the diffuser portion is not limited to being plate-shaped as long as it has a surface that extends from the end of the scroll portion 3e of the scroll portion 3g to the discharge port 6. As shown in FIG. 2(a), the diffuser plate 3c is arranged so as to expand toward the discharge port as viewed from the suction port 5 side with respect to the outer circumferential surface from the beginning of the turn 3d of the peripheral wall 3a facing the diffuser plate 3c to the discharge port configuration point 4. With this configuration, the cross-sectional area of ​​the air passage of the discharge portion 3h gradually expands from the upstream to the downstream, and the air passing through the discharge portion 3h gradually decelerates in speed and the static pressure increases. By making the surface that constitutes the discharge portion 3h the outer circumferential surface of the peripheral wall 3a of the scroll casing 3, the expansion rate of the discharge portion 3h is larger than when a plate is arranged facing the diffuser plate 3c, and the discharge port 6 can be made larger.

[0020] FIG. 3 is a schematic side view showing the shape of the scroll casing 3. The shape of the diffuser plate 3c will be described with reference to FIG. 3. The diffuser plate 3c is formed so as to extend from the end of the roll 3e of the peripheral wall 3a and be continuous with the end of the roll 3e. The length of the diffuser plate 3c from the end of the roll 3e to the end forming the discharge port 6 is the length to the point G where the line L1 overlapping the diffuser plate 3c extended from the end of the roll 3e intersects with the tangent line T of 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 also known that the air flowing through the scroll casing 3 is sufficiently pressurized by setting the angle A between the straight line S connecting the center of the shaft portion 2c and the start of the roll 3d and the straight line L2 passing through the center of the shaft portion 2c and parallel to the diffuser plate 3c to be 0 degrees or more.

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

[0022] As described above, by configuring the discharge port forming point 4 and the diffuser plate 3c, 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 (b), the housing 20 is in the shape of a box having a surface on which the 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 housing 20 is formed is in close contact with a line parallel to the rotation axis RS including the discharge port configuration point 4 on the outer peripheral surface of the peripheral wall 3a. With this configuration, the air discharged from the discharge port 6 of the scroll casing 3 does not enter the inside of the housing 20, but is discharged from the discharge port 20a of the housing 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 housing 20 is formed can prevent the air discharged from the discharge port 6 of the scroll casing 3 from entering the inside of the housing 20, even if it is not a line parallel to the rotation axis RS including the discharge port configuration point 4, as long as it is the outer peripheral surface of the peripheral wall 3a.

[0024] Next, the operation of the centrifugal blower 1 will be described. Air outside the scroll casing 3 is sucked into the scroll casing 3 through the suction port 5. The air sucked into the scroll casing 3 is guided by the bell mouth 7 and sucked into the impeller 2. The air sucked into the impeller 2 becomes an airflow to which dynamic pressure and static pressure are added while passing between the blades 2b, and is blown out toward the radial outside of the impeller 2. The airflow blown out from the impeller 2 is straightened 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. Then, the airflow blown out from the impeller 2 passes through the scroll section 3g, and is blown out of the scroll casing 3 from 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. At this time, 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 follow the sudden expansion of the air passage, causing pressure loss. Or, even when the airflow is discharged from the discharge port 6 to a space such as a room without connecting a duct to the discharge port 6, the airflow cannot follow the sudden expansion of the air passage, causing pressure loss. In the centrifugal blower 1 of the present disclosure, the surface constituting the discharge portion 3h is the outer peripheral surface of the peripheral wall 3a of the scroll casing 3, so that the expansion rate of the discharge portion 3h is larger than that of a plate facing the diffuser plate 3c, and the discharge port 6 can be made larger. Therefore, the pressure loss at the discharge port 6 can be reduced. In addition, by reducing the pressure loss, the power consumption can be reduced relative to the amount of air discharged from the discharge port 6, and a highly efficient centrifugal blower 1 can be obtained.

[0026] As described above, the centrifugal blower 1 in this embodiment has a disk-shaped main plate 2a and a plurality of blades 2b disposed on the peripheral portion of the main plate 2a. The impeller 2 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 is formed in a spiral shape so as to surround the impeller 2 from the radial direction of the rotation axis RS and has an inner circumferential surface facing the impeller 2 and an outer circumferential surface that is the surface opposite the inner circumferential surface. The scroll casing 3 has at least one side wall 3b which covers the impeller 2 from above and in which an inlet 5 for taking in air is formed, a diffuser section which is formed continuously with the spiral 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 which 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 which 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, so that the height of the discharge port 6 of the scroll casing 3 facing downward can be suppressed to be equal to the width of the scroll section 3g, and the discharge port 6 can be made larger than if a plate facing the diffuser plate 3c were disposed. This reduces pressure loss at the discharge port 6, and provides 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 thereof that communicates with the discharge port 6 and houses the scroll casing 3, and a part of the outer circumferential surface of the peripheral wall 3a is in close contact with the inner wall of the housing 20 on one surface thereof 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 be a double-suction type centrifugal blower 1. In the double-suction type centrifugal blower 1, a scroll casing 3 having side walls 3b in which an inlet 5 is formed is provided 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 the double-suction type centrifugal blower 1, the scroll casing 3 has two side walls 3b in which an inlet 5 is formed, 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, a description of the same parts as those in the above-mentioned embodiment will be omitted.

[0031] As shown in FIG. 4, the centrifugal blower 1 of this embodiment is provided with an arc-shaped tongue portion 3f having a constant radius of curvature from a start portion 3d, which is the start of the spiral shape, toward the outer circumferential surface on the peripheral wall 3a of the scroll casing 3. 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 becomes a branching point of the flow path. That is, the air flowing near the end portion 3e of the scroll portion 3g hits the tongue portion 3f and is branched into air flowing into the discharge portion 3h and air flowing into the inside of the peripheral wall 3a and passing through the scroll portion 3g again. The static pressure of the air flowing into the discharge portion 3h increases while passing through the scroll casing 3, and becomes higher than the pressure inside the scroll portion 3g. Therefore, the tongue portion 3f has a function of partitioning such a pressure difference, and also has a function of guiding the air flowing into the discharge portion 3h to each flow path by the curved surface. By having the tongue portion 3f have an appropriate radius of curvature, the air that hits the tongue portion 3f flows smoothly into the discharge portion 3h or the scroll portion 3g, thereby suppressing noise. The appropriate radius of curvature of the tongue portion 3f varies depending on the air volume of the impeller 2 and the size of the scroll casing.

[0032] In order to form the tongue portion 3f having a certain radius of curvature even when 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 portion 3d as shown in FIG. 4. That is, the thickness of the peripheral wall 3a is the distance from a certain point on the outer peripheral surface of the peripheral wall 3a to the inner peripheral surface of a line extending in a direction perpendicular to the tangent of the outer peripheral surface at that point. In particular, in this embodiment, the thickness of the peripheral wall 3a refers to the distance from a certain point on the outer peripheral surface of the peripheral wall 3a from the winding end portion 3e to the discharge port forming point 4 to the inner peripheral surface of a line extending in a direction perpendicular to the tangent of the outer peripheral surface at that point. With this configuration, the scroll casing 3 can be made both lightweight and quiet.

[0033] As described above, the centrifugal blower 1 in this embodiment includes the impeller 2 having a disk-shaped main plate 2a and a plurality of blades 2b disposed on the peripheral portion of the main plate 2a, and rotating about a rotation axis RS that passes through the center of the main plate 2a and is perpendicular to the main plate 2a to generate an airflow, 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 3a that covers the impeller 2 in the axial direction of the rotation axis RS of the impeller 2 and has an inlet 5 for taking in air. a scroll casing 3 having a spiral casing 3b, a diffuser section formed continuously with a 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 airflow in the diffuser section and a part of the outer circumferential 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 circumferential 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 in the vicinity of the end of scroll portion 3e of scroll portion 3g hits tongue portion 3f and is smoothly branched into air that flows into discharge portion 3h and air that flows into the inside of peripheral wall 3a and passes through scroll portion 3g again, thereby suppressing noise. Even if peripheral wall 3a of scroll casing 3 is made of a material thinner than the appropriate diameter of the curvature circle of tongue portion 3f, tongue portion 3f having a constant radius of curvature can be formed, and the scroll casing 3 can be made both lightweight and quiet.

[0035] In addition, the peripheral wall 3a is characterized in that its thickness gradually increases from a part 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 having a constant radius of curvature, and it is possible to achieve both a reduction in weight and a reduction in 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, a description of the same parts as those in the above-mentioned 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 is curved from a start portion 3d, which is the start of the spiral shape, toward the outer circumferential surface. The curved surface of the peripheral wall 3a curved from the start portion 3d toward the outer circumferential surface forms an arc-shaped tongue portion 3f having a constant radius of curvature. By curving the peripheral wall 3a of the scroll casing 3 from the start portion 3d toward the outer circumferential surface, the tongue portion 3f having a constant radius of curvature can be formed even if the peripheral wall of the scroll casing 3 is made of a material thinner than the appropriate diameter of the curvature circle of the tongue portion 3f. Therefore, since the tongue portion 3f has an appropriate radius of curvature, the air that hits the tongue portion 3f flows smoothly into the discharge portion 3h or the scroll portion 3g, thereby suppressing noise.

[0038] As described above, the centrifugal blower 1 in this embodiment has a disk-shaped main plate 2a and a plurality of blades 2b disposed on the peripheral portion of the main plate 2a, the impeller 2 which generates an airflow by rotating about a rotation axis RS which passes through the center of the main plate 2a and is perpendicular to the main plate 2a, the peripheral wall 3a which is formed in a spiral shape so as to surround the impeller 2 in the radial direction of the rotation axis RS and has an inner circumferential surface which faces the impeller 2 and an outer circumferential surface which is the surface opposite to the inner circumferential surface, at least one side wall 3b which covers the impeller 2 in the axial direction of the rotation axis RS of the impeller 2 and in which an inlet 5 for taking in air is formed, and the spiral end of the peripheral wall 3a. and a scroll casing 3 having a diffuser section formed continuously with a downstream end portion 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 airflow in the diffuser section and a part of the outer peripheral surface of the peripheral wall 3a, and through which the airflow generated by the impeller 2 is discharged, wherein the peripheral wall 3a further has an arc-shaped tongue portion 3f extending from the spiral-shaped start portion 3d toward the outer peripheral surface, and twice the radius of curvature of the tongue portion 3f is greater than the thickness of the peripheral wall 3a, and the tongue portion 3f is a curved surface formed by the peripheral wall 3a curving from the start portion 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 circle of curvature of the tongue portion 3f, a tongue portion 3f having a constant radius of curvature can be formed, thereby achieving both a lightweight scroll casing 3 and low noise levels.

[0040] The configurations shown in the above embodiments are examples of the contents of the present invention, and may be combined with other known technologies. Parts of the configurations may be omitted or modified without departing from the gist of the present invention.

[0041] Below, examples of aspects that may be included in the present disclosure are set forth as appendices. (Appendix 1) An impeller having a disk-shaped main plate and a plurality of blades installed on a peripheral portion of the main plate, the impeller rotating about a rotation axis passing through the center of the main plate and 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 a radial direction of the rotating shaft, the peripheral wall having an inner peripheral surface facing the impeller and an outer peripheral surface which is a surface opposite to the inner peripheral surface; at least one side wall covering the impeller from an axial direction of the rotating shaft of the impeller, the side wall having an inlet port for taking in air; a diffuser section formed continuously with the spiral end portion of the peripheral wall, the diffuser section being arranged so that a cross-sectional area of ​​a flow path gradually increases in the direction of the airflow; and a discharge port formed by a downstream end portion of the diffuser section in the airflow and a part of the outer peripheral surface of the peripheral wall, the discharge port for discharging the airflow generated by the impeller; A centrifugal blower equipped with (Appendix 2) The scroll casing further includes a housing having an opening formed on one surface thereof and communicating with the discharge port, and the scroll casing is housed therein. 2. The centrifugal blower of 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 start portion of the spiral shape toward the outer circumferential surface, 3. The centrifugal blower according to claim 1 or 2, 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 peripheral wall has a thickness that gradually increases from a part of the outer circumferential surface toward the beginning of the winding. (Appendix 5) The centrifugal blower according to claim 3, wherein the tongue portion is a curved surface in which the peripheral wall is curved 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 portion, 3 scroll casing, 3a peripheral wall, 3b side wall, 3c diffuser plate, 3d start of roll, 3e end of roll, 3f tongue portion, 3g scroll portion, 3h discharge portion, 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 a peripheral portion of the main plate, the impeller rotating about a rotation axis passing through the center of the main plate and 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 a radial direction of the rotating shaft, the peripheral wall having an inner peripheral surface facing the impeller and an outer peripheral surface which is a surface opposite to the inner peripheral surface; at least one side wall covering the impeller from an axial direction of the rotating shaft of the impeller, the side wall having an inlet port for taking in air; a diffuser section formed continuously with the spiral end portion of the peripheral wall, the diffuser section being arranged so that a cross-sectional area of ​​a flow path gradually increases in the direction of the airflow; and a discharge port formed by a downstream end portion of the diffuser section in the airflow and a part of the outer peripheral surface of the peripheral wall, the discharge port for discharging the airflow generated by the impeller; A centrifugal blower equipped with

2. The scroll casing further includes a housing having an opening formed on one surface thereof and communicating with the discharge port, and the scroll casing is housed therein.

2. The centrifugal blower according to claim 1, wherein a part of the outer circumferential 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 start portion of the spiral shape 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 a thickness of the peripheral wall.

4. 4. The centrifugal blower according to claim 3, wherein the thickness of the peripheral wall gradually increases from the part of the outer circumferential surface toward the beginning of the turn.

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

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