JP6375821B2 - Centrifugal blower and air cleaner equipped with the same - Google Patents

Description

  The present invention relates to a centrifugal blower and an air cleaner equipped with the centrifugal blower.

  Conventionally, a centrifugal blower including an impeller and a casing (a spiral casing) having a spiral inner peripheral surface facing the radially outer side of the impeller is known. In this centrifugal blower, the inner peripheral surface of the casing is circumferential in the circumferential direction from the winding start portion to the winding end portion based on the idea that the average flow velocity of the air in the casing is uniform in each cross section in the casing. It was designed to have a predetermined enlargement ratio (a constant enlargement ratio).

  However, since the flow rate of the fluid flowing out from the gap between the blades of the impeller actually varies depending on the position of the impeller in the circumferential direction, a design with a constant expansion ratio in the circumferential direction is optimal for the actual flow. I can't say there is. As described above, when the flow rate of the fluid flowing out from the impeller and the shape of the casing do not match, noise may increase. Therefore, in order to further reduce the noise of the centrifugal fan, it is necessary to improve the casing shape.

  Patent document 1 is disclosing the centrifugal blower which provided the bulging part which protrudes outward in the vicinity (near winding start part) of the nose part of a casing. Patent Document 2 discloses a centrifugal blower designed so that α is a casing expansion angle at the winding start point of the casing, α is a casing expansion angle near the winding end point, and α <β.

Japanese Utility Model Publication 2-74599 JP-A-61-138900

  In the centrifugal blower of Patent Document 1, a bulging portion is provided in the vicinity of the winding start portion. In this case, since an eddy current is generated in the bulging portion, a sufficient effect of improving the blowing sound (noise) can be obtained. I can't.

  Moreover, in the centrifugal blower of patent document 2, since it continues expanding with the expansion ratio (beta) in the side near a winding end point, the blower outlet of a casing becomes too wide. In this case, when the load of the centrifugal blower increases, the air volume becomes unstable, and there is a problem that it is easy to fall into a surging state in which noise (buzzing sound) is generated. In addition, as an example of the state where the load of the centrifugal blower increases, for example, when the centrifugal blower is used for an air cleaner, a state in which clogging of the filter has progressed can be mentioned.

  The objective of this invention is providing the centrifugal air blower excellent in the noise reduction effect, and an air cleaner provided with the same.

The centrifugal blower of the present invention is a casing having an impeller (5) that rotates about a rotating shaft (A) and a spiral inner peripheral surface (7) facing the radially outer side of the impeller (5) ( 6). The inner peripheral surface (7) includes a first portion (71) along a spiral reference surface (S1) defined by a predetermined enlargement ratio, and an air flow downstream of the first portion (71). A second portion (72) which is a portion on the side and swells radially outward from the reference surface (S1). When the distance between the reference surface (S1) and the rotating shaft (A) is a reference radius (Ra) and the distance between the inner peripheral surface (7) and the rotating shaft (A) is a casing radius (Rb) The maximum portion (72M) where the difference (Rb-Ra) between the casing radius (Rb) and the reference radius (Ra) is the maximum in the second portion (72) is the winding start portion in the casing (6). The winding angle in the circumferential direction from (6S) is at a position larger than 180 degrees, and the downstream side of the curved surface constituting the inner peripheral surface (7) of the casing (6) from the maximum portion (72M) The inner peripheral surface (7) is configured such that the difference (Rb−Ra) up to the winding end (6E), which is the end of the winding, gradually decreases toward the winding end (6E). .

  In the present invention, the maximum portion (72M) where the difference (Rb-Ra) between the casing radius (Rb) and the reference radius (Ra) is maximum is at a position where the winding angle is larger than 180 degrees, and the maximum portion (72M). The difference (Rb-Ra) from the winding end portion (6E) of the casing (6) gradually decreases toward the winding end portion (6E). That is, in the present invention, since the air blowing flow velocity from the gap between the blades of the impeller (5) is large, the region (winding angle of the downstream side in the rotation direction) of the air flow that is likely to cause noise is low. Since the maximum portion (72M) of the difference (Rb-Ra) is provided in a region larger than 180), the blowing flow velocity in this region can be reduced. As a result, the blowing sound can be effectively reduced.

  Moreover, in the present invention, the difference (Rb−Ra) from the maximum portion (72M) to the winding end portion (6E) of the casing (6) is gradually reduced toward the winding end portion (6E). The size of the outlet (42) of (6) is not too large. Thereby, even if the load of the centrifugal blower is increased, it is possible to suppress the air volume from becoming unstable, and thus it is possible to suppress the surging state. As a result, it is possible to suppress the generation of noise (buzzing sound) due to surging.

  Here, in the casing (6) having the spiral inner peripheral surface (7), when the winding start portion (6S) is used as a reference, a region up to 90 degrees from the winding start portion (6S) is defined as a region. The first quadrant, the region from 90 to 180 degrees of wrapping angle is the second quadrant, the region from 180 to 270 degrees of wrapping angle is the third quadrant, and the region downstream of the airflow from 270 degrees is the fourth. Quadrant. Usually, since the blower outlet of a centrifugal blower is provided in the 4th quadrant, the blow-out flow velocity of air in the 4th quadrant (that is, the region downstream of the winding angle of 270 degrees) tends to cause noise.

Therefore, in the centrifugal blower, the first portion (71) is provided from the winding start portion (6S) or the vicinity thereof to at least the position where the winding angle is 180 degrees, and the second portion (72) is The portion (72S) that starts to bulge radially outward from the reference surface (S1) is located at a position where the winding angle is larger than 180 degrees and smaller than 270 degrees, and the maximum from the portion (72S) that begins to bulge. the difference to the site (72M) (Rb-Ra) has been configured to gradually increase.

In this configuration, the part (72S) where the second portion (72) starts to bulge is provided in the third quadrant adjacent to the fourth quadrant, and the difference (Rb-Ra) from the part (72S) where the bulge starts to the maximum part (72M). ) Gradually increases. Thereby, the blowing flow velocity in the fourth quadrant can be effectively reduced. On the other hand, the first quadrant and the second quadrant are provided with a first portion (71), that is, a portion along the reference plane (S1). That is, in the first quadrant and the second quadrant that do not contribute much to the reduction of the blowout flow velocity in the fourth quadrant, the inner peripheral surface (7) is not expanded radially outward. Thereby, since it can suppress that a casing (6) becomes unnecessarily large, it can suppress that a casing (6) becomes large.
In the present invention, the winding end portion (6E) includes the reference surface (S1) from the winding start portion (6S) to the winding end portion (6E) from the inner peripheral surface (7) of the casing (6). ) In the radial direction outside the downstream end (E1) of the reference surface (S1).

  In the centrifugal fan, the maximum part (72M) preferably has a winding angle in a range of 270 ° ± 10 °.

  By providing the maximum portion (72M) in the range where the winding angle is 270 ° ± 10 ° as in this configuration, the blowout flow velocity from the impeller (5) can be increased intensively in this range. Thereby, as shown in the numerical analysis result shown in FIG. 4 to be described later, in the fourth quadrant which is a region further downstream than this range and is likely to cause noise, the impeller (5) The blowing flow rate can be effectively reduced.

  In the centrifugal blower, the casing (6) has a blow diffuser portion (62) extending further downstream from the winding end portion (6E), and an inner surface of the blow diffuser portion (62) is the winding end portion. (6E) is a plane extending in the tangential direction of the inner peripheral surface (7), and the outlet (42) of the blowout diffuser portion (62) is the same as the inner peripheral surface (7) of the casing (6). It is preferable that it is the same size as the blowout port of the blowout diffuser part when it is assumed that it extends along the reference plane (S1) from the winding start part (6S) to the winding end part (6E).

  In this structure, the blower outlet (42) of the blowout diffuser part (62) has the inner peripheral surface (7) of the casing (6) from the winding start part (6S) to the winding end part (6E) to the reference plane (S1). It is the same size as the blowout port of the blowout diffuser when it is assumed to be along. Therefore, in this configuration, even if the second portion (72) swelled radially outward from the reference surface (S1) is provided on the spiral inner peripheral surface (7), the air outlet (62) of the air diffuser portion (62) ( The size of 42) can be made the same as the size of the air outlet when the second portion (72) is not provided. Thereby, even if the load of a centrifugal blower becomes large, it can suppress effectively that air volume becomes unstable.

  The air cleaner of the present invention includes a case having an air inlet and an air outlet, the above-described centrifugal blower for forming an air flow from the air inlet to the air outlet in the case, and the inside of the case And a cleaning unit for cleaning the air flowing through the.

  In this structure, since the air cleaner is equipped with the centrifugal blower as described above, the blowing sound can be effectively reduced. Moreover, even if the load of the centrifugal blower increases due to, for example, clogging of the filter in the air cleaner, it is possible to suppress the air volume from becoming unstable. Thereby, it can suppress that it will be in the surging state which noise (buzzing sound) generate | occur | produces.

  As described above, according to the present invention, noise in the centrifugal fan can be effectively reduced.

It is sectional drawing which shows the air cleaner provided with the centrifugal blower which concerns on one Embodiment of this invention. It is a perspective view which shows the centrifugal blower which concerns on embodiment. It is a front view which shows the centrifugal blower which concerns on embodiment. It is a figure which shows the result of having calculated | required the flow velocity distribution of the air which blows off from an impeller by the numerical analysis in the centrifugal air blower which concerns on embodiment. It is sectional drawing which shows the casing of the centrifugal blower which concerns on embodiment. It is a graph which shows the relationship between the winding angle in the internal peripheral surface of the casing of the centrifugal blower which concerns on embodiment, and a casing radius. It is the figure which expanded the part enclosed with the broken line in FIG. In the centrifugal blower which concerns on a reference example, it is a figure which shows the result of having calculated | required the flow velocity distribution of the air which blows off from an impeller by numerical analysis. It is a figure which shows the result of having compared the spectrum of the blowing sound in the centrifugal blower which concerns on embodiment, and the centrifugal blower which concerns on a reference example. It is sectional drawing which shows the casing of the centrifugal blower which concerns on the modification of embodiment.

  Hereinafter, a centrifugal blower 4 according to an embodiment of the present invention and an air cleaner 1 having the same will be described in detail with reference to the drawings.

[Overall structure of air cleaner]
FIG. 1 is a cross-sectional view showing an air cleaner 1 including a centrifugal blower 4 according to an embodiment of the present invention. The air cleaner 1 has a function of purifying indoor air by sucking air in the indoor space and removing dust and the like, and blowing the cleaned air into the indoor space. The air cleaner 1 is attached to, for example, an indoor floor or an indoor wall. As shown in FIG. 1, the air purifier 1 includes a case 2 having an air inlet 21 and an air outlet 22, and a centrifugal blower that forms an air flow from the air inlet 21 to the air outlet 22 in the case 2. 4 and a cleaning unit 3 that cleans the air flowing in the case 2.

  The case 2 of the air cleaner 1 is a box that can accommodate the centrifugal blower 4 and the cleaning unit 3. In the present embodiment, the air inlet 21 is formed on the side surface of the case 2 and the air outlet 22 is formed on the upper surface of the case 2. The positions of the air inlet 21 and the air outlet 22 are shown in FIG. It is not limited to the position.

  The cleaning unit 3 includes one or a plurality of units such as a filter unit, an electric dust collection unit, and a deodorizing unit. In the specific example shown in FIG. 1, in the cleaning unit 3, the filter unit 31 and the electrostatic dust collection unit 32 are arranged along the air flow.

  The filter unit 31 captures relatively large dust in the air. The filter member of the filter unit 31 is formed in a shape such as a band shape or a sheet shape, for example. The electric dust collection unit 32 electrically collects relatively small dust in the air. The electric dust collection unit 32 includes, for example, an unillustrated ionization unit and a dust collection unit. The ionization unit has a charging unit that charges dust in the air by plasma discharge or the like. The dust collection unit electrically attracts and captures the dust charged in the ionization unit. Examples of the deodorizing unit include a unit having a deodorizing element including activated carbon, but are not limited thereto.

  When the centrifugal blower 4 is driven, room air is sucked into the case 2 from the air inlet 21. The air sucked into the case 2 is cleaned by removing dust, odor components and the like in the cleaning unit 3. The purified air is blown out from the air outlet 22 into the indoor space.

[Centrifuge blower]
As shown in FIGS. 1, 2, and 3, the centrifugal blower 4 is a multiblade fan (sirocco fan). The centrifugal blower 4 includes a casing 6 having an inlet 41 and an outlet 42 and an impeller 5 accommodated in the casing 6. The impeller 5 rotates around the rotation axis A (see FIGS. 2 and 4). When the impeller 5 rotates, air is taken into the casing 6 from the suction port 41 and flows out radially from the gap between the blades 51 of the impeller 5 radially outward of the impeller 5. The air that has flowed out flows through the spiral flow path between the impeller and the casing 6 to the downstream side, and is blown out of the casing 6 through the air outlet 42.

  The impeller 5 includes a plurality of blades 51 arranged along the circumferential direction and a holding ring 52 that holds the plurality of blades 51. For example, the holding rings 52 are provided at both ends of the plurality of blades 51 in the axial direction. As shown in FIG. 4, the plurality of blades 51 are forward blades whose blade outlets are inclined in the rotation direction D.

  The casing 6 of the centrifugal blower 4 is a spiral casing (volute casing) that collects air that has flowed radially outward from the impeller 5 and that guides it to the air outlet 42 of the casing 6. As shown in FIGS. 2 and 3, the casing 6 uses, for example, a peripheral plate 64 that is curved to form a shape surrounding the impeller 5 using, for example, a belt-like plate material, and a flat plate material, for example. And a pair of side plates 65 that close both side openings of the peripheral plate 64 are joined to each other. Each side plate 65 is formed with a bell mouth-shaped suction port 41.

  As shown in FIGS. 2, 4, and 5, the casing 6 includes a scroll portion 61 (scroll diffuser portion 61) provided so as to surround the impeller 5, and an outlet diffuser portion 62 in which the outlet 42 is formed. Have

  As shown in FIGS. 4 and 5, the scroll portion 61 has an inner peripheral surface 7 that faces the impeller 5 radially outward. The inner peripheral surface 7 of the scroll portion 61 is a curved surface that smoothly curves along the circumferential direction of the impeller 5 from the winding start portion 6S to the winding end portion 6E. The winding start portion 6S is an upstream edge of the inner peripheral surface 7 which is a curved surface, and the winding end portion 6E is a downstream edge of the inner peripheral surface 7 which is a curved surface.

  As shown in FIGS. 4 and 5, the inner peripheral surface 7 of the scroll portion 61 is a first portion 71 along the spiral reference surface S <b> 1 and a portion on the downstream side of the air flow from the first portion 71. The second portion 72 (the bulging portion 72) swells radially outward from the reference plane S1. The first portion 71 and the second portion 72 constitute an inner circumferential surface 7 that is smoothly curved. In the present embodiment, the second portion 72 (the bulging portion 72) is provided in the vicinity of the winding end portion 6E.

  The reference surface S1 is a spiral curved surface defined by a predetermined enlargement factor (a constant enlargement factor). Examples of the spiral reference surface S1 defined at a predetermined magnification include a reference surface S1 based on an Archimedes spiral, a reference surface S1 based on a logarithmic spiral, and the like. In the specific example shown in FIG. 6, the reference plane S1 is defined by an Archimedean spiral. In the case of the Archimedes spiral, the enlargement ratio α (enlargement angle α) that defines the reference plane S1 is, as shown in FIG. 6, an inclination of a graph with the winding angle (θ) on the horizontal axis and the radius on the vertical axis. The angle α. In the graph of FIG. 6, “R0” is the reference radius Ra of the reference surface S1 at the winding start portion 6S. In FIG. 6, the solid line indicates the inner peripheral surface 7 (first portion 71 and second portion 72) of the scroll portion 61, and the broken line indicates the reference surface S1.

  As shown in FIG. 5, the reference radius Ra is a distance between the reference surface S <b> 1 and the rotation axis A in a cross section orthogonal to the rotation axis A in the casing 6. The casing radius Rb is a distance between the inner peripheral surface 7 and the rotation axis A in a cross section orthogonal to the rotation axis A in the casing 6.

  As shown in FIG. 5, the winding start portion 6 </ b> S of the casing 6 is a tongue portion 66 of the casing 6 or a portion in the vicinity thereof. The tongue portion 66 is a convex portion provided at a boundary portion between the scroll portion 61 and the blowout diffuser portion 62. The tongue 66 extends in a direction parallel to the rotation axis A in the casing 6.

  As shown in FIG. 5, when the inner surface of the tongue 66 (the surface facing the impeller 5) is an arcuate curved surface, the winding start portion 6S may be positioned as shown in FIG. it can. A circle C indicated by an alternate long and short dash line in FIG. 7 is a circle in contact with the inner surface of the tongue 66 (for example, a circle having the same radius as the curvature radius at the tip (top) of the inner surface of the tongue 66). The winding start portion 6S can be a portion where a straight line L1 connecting the center of the circle C and the rotation axis A intersects the inner surface of the tongue portion 66. In addition, when the inner surface of the tongue 66 is not an arcuate curved surface, for example, the inner surface of the tongue 66 has a sharp shape, the sharp tip can be used as the winding start portion 6S.

  As shown in FIG. 5, the winding end portion 6 </ b> E of the casing 6 is an end portion on the downstream side (air outlet 42 side) of the air flow on the inner peripheral surface 7 of the scroll portion 61. That is, the winding end portion 6E is a boundary portion between the inner peripheral surface 7 of the scroll portion 61 and a first inner surface 621 of a blowout diffuser portion 62 described later. Specifically, in the present embodiment, the inner peripheral surface 7 of the scroll portion 61 is a curved surface, and the first inner surface 621 of the blowout diffuser portion 62 is a flat surface, so that the winding end portion 6E is downstream of the curved surface 7. It is a side end portion and a boundary portion between the curved surface 7 and the flat surface 621.

  In the present embodiment, the winding angle θ (the angle in the circumferential direction from the winding start portion 6S in the casing 6) is as follows. That is, in the cross-sectional view shown in FIG. 5, the winding angle θ at an arbitrary position of the inner peripheral surface 7 of the casing 6 (the inner peripheral surface 7 of the scroll portion 61) is a straight line L1 passing through the rotation axis A and the winding start portion 6S. , An angle formed by the rotation axis A and a straight line passing through the arbitrary position.

  When the winding start portion 6S is used as a reference in the cross section of the casing 6 shown in FIG. 5, the inside of the casing 6 can be divided into four regions (first quadrant to fourth quadrant). The first quadrant is a region where the winding angle is 90 degrees from the winding start portion 6S, and is a region between the two-dot chain line straight line L1 and straight line L2. The second quadrant is a region where the winding angle is 90 degrees to 180 degrees, and is a region between the two-dot chain line straight line L2 and straight line L3. The third quadrant is an area where the winding angle is 180 degrees to 270 degrees, and is an area between the two-dot chain line straight line L3 and straight line L4. The fourth quadrant is a region where the winding angle is larger than 270 degrees, and is a region closer to the outlet 42 than the two-dot chain line L4.

  As shown in FIG. 5, in this embodiment, the scroll part 61 is provided in the 1st quadrant, the 2nd quadrant, and the 3rd quadrant, and also provided in a part of the 4th quadrant. The blowout diffuser portion 62 is provided on the downstream side of the scroll portion 61 in the fourth quadrant.

  As shown in FIG. 4, the scroll portion 61 has an air flow path 61 </ b> F on the radially outer side than the impeller 5. The cross-sectional area of the flow path 61F of the scroll part 61 gradually increases from the winding start part 6S or the vicinity thereof to the winding end part 6E or the vicinity thereof toward the downstream side (air outlet 42 side) of the air flow. In the present embodiment, the flow path 61F gradually increases in cross-sectional area from the winding start portion 6S to the maximum portion 72M described later as it goes downstream, but is not limited thereto. For example, even if the bulging portion 72 is provided as in the present embodiment, the cross-sectional area of the flow path 61F may gradually increase from the winding start portion 6S to the winding end portion 6E.

  The blowout diffuser part 62 has a flow path 62F connected to the flow path 61F on the downstream side of the flow path 61F of the scroll part 61.

  As shown in FIGS. 2 and 3, the blowout diffuser portion 62 includes a first inner surface 621 connected to the inner peripheral surface 7 of the scroll portion 61 (specifically, the second portion 72 of the inner peripheral surface 7), It has the 2nd inner surface 622 which opposes the 1st inner surface 621 at intervals and the 1st inner surface 621, and the inner surfaces 623 and 624 which connect both sides of these inner surfaces 621 and 622. The four inner surfaces 621, 622, 623, and 624 of the blowout diffuser portion 62 form a flow path 62 </ b> F (see FIG. 4) of the blowout diffuser portion 62. The downstream side end portions of the inner surfaces 621, 622, 623, and 624 form the air outlet 42 of the casing 6 (the air outlet 42 of the outlet diffuser portion 62).

  The first inner surface 621 of the blowout diffuser portion 62 extends further from the winding end portion 6E on the inner peripheral surface 7 of the scroll portion 61 to the downstream side of the air flow. The first inner surface 621 of the blowout diffuser portion 62 is a plane extending in the tangential direction of the inner peripheral surface 7 at the winding end portion 6E in the cross section (cross section orthogonal to the rotation axis A) shown in FIG.

  The second inner surface 622 of the blowout diffuser portion 62 is a plane adjacent to the tongue portion 66. The second inner surface 622 is inclined with respect to the first inner surface 621 so that the distance from the first inner surface 621 gradually increases toward the air outlet 42. Therefore, the cross-sectional area of the flow channel 62F of the blowout diffuser portion 62 gradually increases toward the blowout port 42 in the vicinity of the blowout port 42.

  In this embodiment, it is assumed that the air outlet 42 of the outlet diffuser portion 62 has the inner peripheral surface 7 of the casing 6 along the reference plane S1 indicated by a broken line in FIG. 5 from the winding start portion 6S to the winding end portion 6E. Is located at the same position as the air outlet (virtual air outlet) of the outlet diffuser section.

  Specifically, as shown in FIG. 5, the downstream end E1 of the reference surface S1, which is a curved surface, is at a position corresponding to the winding end portion 6E on the inner peripheral surface 7 of the casing 6, and the reference surface S1 (first A second reference surface S2 extends further downstream from the downstream end E1 of the first reference surface S1). The second reference plane S2 is a plane extending in the tangential direction of the reference plane S1 at the downstream end E1 of the reference plane S1 in the cross section shown in FIG. In the present embodiment, the downstream end 621E of the first inner surface 621 of the blowout diffuser portion 62 coincides with the downstream end E2 of the second reference plane S2.

  Therefore, the blower outlet 42 of the blower diffuser part 62 is the same size as the virtual blower outlet mentioned above, and is the same size as the blower outlet 142 in the reference example shown in FIG. Thereby, in this embodiment, even if the 2nd part 72 which swelled to radial direction outer side than the reference plane S1 in the spiral inner peripheral surface 7 is provided, the magnitude | size of the blower outlet 42 of the blowing diffuser part 62 is made into 1st. The size of the air outlet (virtual air outlet) when the two portions 72 are not provided can be the same. Thereby, even if the load of the centrifugal blower 4 increases, it is possible to effectively suppress the air volume from becoming unstable.

  Of the inner peripheral surface 7 of the scroll portion 61, the first portion 71 along the reference surface S1 is provided from the winding start portion 6S or its vicinity to a position where the winding angle θ is at least 180 degrees. In the present embodiment, the first portion 71 is provided from the winding start portion 6S to a position at a winding angle of 200 degrees as shown in FIG. 5, but is not limited thereto.

  In the second portion 72 (the bulging portion 72), a portion 72S (the bulging portion start point 72S) that starts to bulge radially outward from the reference plane S1 is at the position of the winding angle θ1 shown in FIGS. The winding angle θ1 is preferably a value larger than 180 degrees and smaller than 270 degrees, and more preferably 180 degrees or more and 220 degrees or less. In the graph shown in FIG. 6, the portion 72 </ b> S that starts to bulge is exemplified as a case where the winding angle θ <b> 1 is at a position of 200 degrees, but is not limited thereto.

  In the second portion 72 (the bulging portion 72), the maximum portion 72M where the difference (Rb−Ra) between the casing radius Rb and the reference radius Ra is maximum is at the position of the winding angle θ2 shown in FIG. The winding angle θ2 is larger than 180 degrees. The winding angle θ of the maximum portion 72M is preferably in the range of 270 ° ± 10 °. In the graph shown in FIG. 6, the maximum part 72 </ b> M illustrates a case where the winding angle θ <b> 1 is at a position of 270 degrees, but is not limited thereto.

  The casing radius Rb, the reference radius Ra, and the enlargement ratio (Rb / Ra) at the maximum portion 72M are not particularly limited, but can be set, for example, in the range of 1.02 to 1.15. In the graph shown in FIG. 6, the enlargement ratio (Rb / Ra) is about 1.05, but is not limited to this.

  In the present embodiment, in the second portion 72, the difference (Rb−Ra) between the casing radius Rb and the reference radius Ra gradually increases from the portion 72S starting to bulge toward the maximum portion 72M. It becomes smaller gradually toward the winding end portion 6E. However, the maximum portion 72M may be a region having a certain width in the circumferential direction.

  FIG. 8 is a diagram showing the results of numerical analysis of the flow velocity distribution of air blown out from the impeller 105 in the centrifugal blower 104 according to the reference example. The centrifugal blower 104 of the reference example shown in FIG. 8 has the same structure except that the shape of the casing 106 is different from the centrifugal blower 4 of the present embodiment shown in FIG. The casing 106 in the reference example has a scroll part 161 and a blowout diffuser part 162. The scroll portion 161 has a spiral inner peripheral surface 107 that faces the radially outer side of the impeller 105. The inner peripheral surface 107 is a spiral curved surface defined by the same magnification as the first portion 71 of the inner peripheral surface 7 in the present embodiment shown in FIG. 4 from the winding start portion 106S to the winding end portion 106E. is there. That is, the entire inner peripheral surface 107 in the reference example is formed with a constant enlargement ratio.

  In the flow velocity distribution by numerical analysis shown in FIGS. 4 and 8, the flow velocity of air is represented by a vector, and the longer the arrow and the darker the color, the larger the flow velocity.

  In the centrifugal blower 104 of the reference example, as shown in FIG. 8, the flow velocity of the air flowing out from the impeller 105 in another region (for example, the first quadrant to the third quadrant) is close to the blowout port 142 (fourth quadrant). It can be seen that it is much larger than the flow velocity at.

  On the other hand, in the centrifugal blower 4 of the present embodiment, since the bulging portion 72 (second portion 72) is provided on the inner peripheral surface 7 of the scroll portion 61, as shown in FIG. It can be seen that the flow velocity of the air flowing out from the impeller 5 in the region (fourth quadrant) is lower than the corresponding region in the reference example shown in FIG. That is, in this embodiment, the maximum flow velocity of the air blown from the impeller 5 in the region close to the air outlet 42 is compared with the maximum flow velocity of the air blown from the impeller 105 in the region close to the air outlet 142 in the reference example. Is falling.

  The reason why the maximum flow velocity is reduced in the present embodiment is as follows. That is, in the present embodiment, by providing the bulging portion 72 on the upstream side of the winding end portion 6E and in the vicinity of the winding end portion 6E (the range of the winding angle of 270 degrees ± 10 degrees), the gap between the blades 51 is eliminated. The blowout flow velocity is reduced in the region downstream of the rotation direction from the vicinity of the winding angle of 270 °, which is likely to cause noise, and the blowing noise can be reduced. This is because the pressure distribution in the casing 6 changes due to the presence of the bulging portion 72, and air is blown out slightly upstream from the region of the maximum flow velocity (that is, near the maximum portion 72M of the bulging portion 72). This is because the amount increased and the maximum flow rate decreased relatively.

  When the maximum flow velocity of the air blown out from the impeller 5 is lowered in the region close to the air outlet 42 as in the present embodiment, the noise in the region of 1000 Hz or more is reduced as shown in FIG. In the spectrum analysis result shown in FIG. 9, the blowing sound of the present embodiment is lowered by 0.6 dBA compared to the blowing sound of the reference example. Noise in the region of 1000 Hz or more is noise generated by fine vortices with a large flow velocity.

[Summary of Embodiment]
As described above, in the present embodiment, the maximum portion 72M at which the difference (Rb−Ra) between the casing radius Rb and the reference radius Ra is maximum is at a position where the winding angle is larger than 180 degrees, and the casing is separated from the maximum portion 72M. The difference (Rb−Ra) up to the winding end portion 6E of 6 gradually decreases toward the winding end portion 6E. That is, in this embodiment, since the air blowing speed from the gap between the blades of the impeller 5 is large, the region (winding angle is 180 °) on the downstream side (downstream in the rotational direction) of the air flow that is likely to cause noise. Since the maximum portion 72M of the difference (Rb−Ra) is provided in the larger region), the blowout flow velocity in this region can be reduced. As a result, the blowing sound can be effectively reduced.

  In addition, in this embodiment, the difference (Rb−Ra) from the maximum portion 72M to the winding end portion 6E of the casing 6 gradually decreases as it goes toward the winding end portion 6E. Is not too wide. Thereby, even if the load of the centrifugal blower 4 is increased, it is possible to suppress the air volume from becoming unstable, and thus it is possible to suppress the surging state. As a result, it is possible to suppress the generation of noise (buzzing sound) due to surging.

  In the centrifugal blower 4, the first portion 71 is provided from the winding start portion 6S or the vicinity thereof to at least a position where the winding angle is 180 degrees, and the second portion 72 is located on the radially outer side from the reference plane S1. The part 72S that starts to swell is located at a position where the winding angle is larger than 180 degrees and smaller than 270 degrees, and the difference (Rb−Ra) gradually increases from the part 72S that starts to swell to the maximum part 72M.

  Thereby, the blowing flow velocity in the fourth quadrant can be effectively reduced. On the other hand, a first portion 71, that is, a portion along the reference plane S1 is provided in the first quadrant and the second quadrant. That is, in the first quadrant and the second quadrant that do not contribute much to the reduction of the blowout flow velocity in the fourth quadrant, the inner peripheral surface 7 is not expanded outward in the radial direction. Thereby, since it can suppress that the casing 6 becomes unnecessarily large, it can suppress that the casing 6 becomes large.

  In the centrifugal blower 4, the maximum portion 72M preferably has a winding angle in a range of 270 ° ± 10 °. By providing the maximum portion 72M in the range where the winding angle is 270 degrees ± 10 degrees as in this configuration, the blowout flow velocity from the impeller 5 can be increased intensively in this range. As a result, as shown in the numerical analysis results to be described later shown in FIG. 4, the blowout flow velocity from the impeller 5 in the fourth quadrant which is a region further downstream than this range and is likely to cause noise. Can be effectively reduced.

  In the centrifugal blower 4, the casing 6 has an outlet diffuser portion 62 that extends further downstream from the winding end portion 6E, and an inner surface 621 of the outlet diffuser portion 62 extends in a tangential direction of the inner peripheral surface 7 at the winding end portion 6E. The air outlet 42 of the air outlet diffuser 62 is a flat air outlet when the inner peripheral surface 7 of the casing 6 is assumed to be along the reference plane S1 from the winding start portion 6S to the winding end portion 6E. Is the same size. Therefore, even if the second portion 72 swelled radially outward from the reference surface S1 on the spiral inner peripheral surface 7 is provided, the size of the outlet 42 of the blowout diffuser portion 62 is set to the second portion 72. The size can be the same as the size of the outlet when there is not. Thereby, even if the load of the centrifugal blower 4 increases, it is possible to effectively suppress the air volume from becoming unstable.

[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to these embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the meaning.

  FIG. 10 is a cross-sectional view showing the casing 6 of the centrifugal blower 4 according to a modification of the embodiment. In the modification shown in FIG. 10, the shape of the portion in the vicinity of the winding start portion 6 </ b> S in the inner peripheral surface 7 of the casing 6 is different from that in the embodiment shown in FIG. 5, and other configurations are the embodiment shown in FIG. 5. Is the same.

  In the modification shown in FIG. 10, the casing 6 has a short flat surface portion P (a straight portion in FIG. 10) adjacent to the tongue portion 66. The casing radius Rb hardly changes in the plane portion P, and the casing radius Rb gradually increases in the first portion 71 on the downstream side of the plane portion P. The first portion 71 is a curved surface along a spiral reference surface S1 defined by a predetermined enlargement ratio, as in the embodiment shown in FIG. The plane portion P is the closest portion between the impeller 5 and the casing 6. With such a configuration, noise generated by the interference between the tongue 66 and the blades 51 can be further reduced, so that the centrifugal blower 4 that is quieter can be manufactured in combination with the effect of the bulging portion 72. it can. Even when the flat surface portion P is provided adjacent to the tongue portion 66 as in the modification shown in FIG. 10, the winding start portion 6S is set at the same position as that shown in FIG. For the flat portion P, for example, a configuration as described in JP-A-2003-035298 can be employed.

  In the said embodiment, although the case where a centrifugal air blower was applied to the air cleaner 1 was illustrated, it is not restricted to this. The centrifugal blower of the embodiment can be applied to an air conditioner that performs at least one of a cooling operation, a heating operation, a dehumidifying operation, and a humidifying operation, for example.

  In the above embodiment, as the centrifugal blower, the double suction type in which air is sucked into the casing from both sides in the axial direction is exemplified, but the present invention is not limited to this, and the single suction type in which air is sucked into the casing from only one side in the axial direction. There may be.

  In the said embodiment, the blower outlet 42 of the blower diffuser part 62 is the blower of a blower diffuser part in the case where it is assumed that the inner peripheral surface 7 of the casing 6 is along the reference plane S1 from the winding start part 6S to the winding end part 6E. Although the case where it was the same magnitude | size as an exit (virtual blower outlet) was illustrated, it is not restricted to this, The magnitude | size of the blower outlet 42 may be smaller than a virtual blower outlet, and larger than a virtual blower outlet May be. That is, the downstream end portion 621E of the first inner surface 621 of the blowout diffuser portion 62 may not coincide with the downstream end portion E2 in the second reference surface S2.

1 Air Purifier 2 Air Purifier Case 21 Air Purifier Case Air Inlet 22 Air Purifier Case Air Outlet 3 Cleaner 4 Centrifugal Blower 41 Centrifugal Blower Inlet 42 Centrifugal Blower Outlet 5 Impeller 51 Blade 6 Centrifugal blower casing 6S Winding start part 6E Winding end part 61 Casing scroll part 61F Flow path of scroll part 62 Blowing diffuser part of casing 62F Flow path of blowing diffuser part 621 Inside surface of blowing diffuser part (first Inside)
66 Tongue 7 Inner peripheral surface of casing 71 First portion of inner peripheral surface 72 Second portion of inner peripheral surface (bulging portion)
72S Part of the second part (bulging part) starting to bulge 72M Maximum part of the second part (bulging part) A Rotating shaft Ra Reference radius Rb Casing radius S1 First reference surface S2 Second reference surface α Inner circumferential surface of the casing Enlargement ratio θ Winding angle θ1 Winding angle at the portion where the second portion begins to bulge θ2 Winding angle at the maximum portion of the second portion θ3 Winding angle at the end of winding of the casing

Claims (4)

An impeller (5) that rotates about a rotation axis (A);
A casing (6) having a spiral inner peripheral surface (7) facing the radially outer side of the impeller (5),
The inner peripheral surface (7) includes a first portion (71) along a spiral reference surface (S1) defined by a predetermined enlargement ratio, and an air flow downstream of the first portion (71). A second portion (72) which is a side portion and swells radially outward from the reference surface (S1),
When the distance between the reference surface (S1) and the rotating shaft (A) is a reference radius (Ra) and the distance between the inner peripheral surface (7) and the rotating shaft (A) is a casing radius (Rb) The maximum portion (72M) where the difference (Rb-Ra) between the casing radius (Rb) and the reference radius (Ra) is the maximum in the second portion (72) is the winding start portion in the casing (6). The winding angle in the circumferential direction from (6S) is at a position larger than 180 degrees, and the downstream side of the curved surface constituting the inner peripheral surface (7) of the casing (6) from the maximum portion (72M) the winding end portion is an end portion (6E) said difference in until (Rb-Ra), so that gradually decreases toward the winding end portion (6E), the inner peripheral surface (7) is constituted ,
The first portion (71) is provided from the winding start portion (6S) or the vicinity thereof to at least the position where the winding angle is 180 degrees,
In the second portion (72), a portion (72S) that starts to bulge radially outward from the reference surface (S1) is located at a position where the winding angle is larger than 180 degrees and smaller than 270 degrees, and the bulging is performed. The difference (Rb−Ra) is configured to gradually increase from the starting portion (72S) to the maximum portion (72M),
In the winding end portion (6E), the inner peripheral surface (7) of the casing (6) is along the reference surface (S1) from the winding start portion (6S) to the winding end portion (6E). A centrifugal blower located on the radially outer side of the downstream end (E1) of the reference surface (S1) when assumed . The centrifugal blower according to claim 1, wherein the maximum portion (72M) has a winding angle in a range of 270 degrees ± 10 degrees. The casing (6) has a blowout diffuser portion (62) extending further downstream from the winding end portion (6E),
The inner surface of the blowout diffuser portion (62) is a plane extending in the tangential direction of the inner peripheral surface (7) at the winding end portion (6E),
The blowout port (42) of the blowout diffuser part (62) is configured so that the inner peripheral surface (7) of the casing (6) extends from the winding start part (6S) to the winding end part (6E). The centrifugal blower according to claim 1 or 2 , wherein the blower has the same size as the blowout port of the blowout diffuser portion when it is assumed that the blower is along the same line. A case (2) having an air inlet (21) and an air outlet (22);
The centrifugal blower (4) according to any one of claims 1 to 3 , wherein an air flow from the air inlet (21) to the air outlet (22) is formed in the case (2).
And an air purifier (3) for purifying air flowing in the case (2).