Centrifugal fan and air conditioner equipped with same

Abstract

To provide a centrifugal fan capable of uniforming the wind speed distribution of the blown airflow. [Solution] This turbofan includes a hub 120 to which a motor shaft serving as a rotation axis is fixed at the center, an annular shroud 130 disposed opposite the hub 120, and a plurality of blades 140 connecting the shroud 130 and the hub 120. The shroud 130 has a groove 136 recessed in the direction of the rotation axis on the surface facing the hub 120, and the groove 136 is formed around the entire circumference on the inner periphery of the shroud 130.

Description

[Technical Field]

[0001] The present invention relates to a centrifugal fan and an air conditioner equipped with the same. [Background technology]

[0002] A centrifugal fan installed in an indoor unit of an air conditioner generates an airflow in a ventilation duct connecting the indoor unit's air inlet and outlet by rotating. In centrifugal fans, a shroud is generally positioned adjacent to a bellmouth (see, for example, Patent Document 1). According to Patent Document 1, the shroud has an arc-shaped cross section and bends the air drawn into the centrifugal fan and flowing in the direction of the motor's rotation shaft in a centrifugal direction (outer periphery) and sends the airflow to a heat exchanger positioned around the centrifugal fan. Furthermore, by reducing the gap between the shroud and the bellmouth, the shroud also serves to prevent the air blown out from the centrifugal fan from flowing back through the gap, thereby improving airflow efficiency. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-190415 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the shroud with an arc-shaped cross section in the centrifugal fan disclosed in Patent Document 1 is not very effective at bending the airflow outward, so the airflow tends to be biased toward the hub, which faces the shroud. This results in an uneven air velocity distribution, with the air velocity higher on the hub side and lower on the shroud side. As a result, the airflow passing through the heat exchanger varies in speed, increasing ventilation resistance in areas of the heat exchanger where high-speed airflow passes and degrading heat exchange performance in areas where low-speed airflow passes.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a centrifugal fan that can uniformize the wind speed distribution of the airflow that is blown out, and an air conditioner equipped with the same. [Means for solving the problem]

[0006] The present invention is a centrifugal fan comprising: a hub having a motor shaft fixed to its center, which serves as a rotation axis; an annular shroud arranged opposite the hub; and a plurality of blades connecting the shroud and the hub, wherein the shroud has a groove recessed in the direction of the rotation axis on the surface facing the hub, and the groove is formed around the entire inner circumference of the shroud. [Effects of the Invention]

[0007] According to the present invention, the wind speed distribution of the airflow blown out from the centrifugal fan can be made uniform. Furthermore, by installing the centrifugal fan of the present invention in an air conditioner, the heat exchange capacity of the air conditioner can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing an air conditioner equipped with a turbofan according to a first embodiment of the present invention. [Figure 2] 1 is a perspective view showing a turbofan according to a first embodiment of the present invention. [Figure 3] 1 is a perspective view showing a cross section of a portion of a turbofan according to a first embodiment. [Figure 4] FIG. 6 is a cross-sectional view taken along line IV-IV in FIG. 5. [Figure 5] 1A is a perspective view showing a cross section of a part of the turbofan of the first embodiment, and FIG. 1B is an enlarged view of a part indicated by an arrow B in FIG. 1A. [Figure 6] FIG. 4 is a perspective view showing a turbofan according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a perspective view of the turbofan of the second embodiment, taken along line XX in FIG. 9, showing a shroud. [Figure 8]FIG. 6 is a perspective view showing a cross section of a part of a turbofan according to a second embodiment. [Figure 9] 10A is a perspective view showing a cross section of a part of a turbofan according to a second embodiment, and FIG. 10B is an enlarged view of a part indicated by an arrow B in FIG. [Figure 10] 10 is a cross-sectional view taken along line XX in FIG. 9. [Figure 11] FIG. 6 is a perspective view showing a cross section of a part of a turbofan according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [1] First embodiment 1. Air conditioner configuration FIG. 1 is a vertical cross-sectional view showing the configuration of a turbofan (centrifugal fan) 100 according to a first embodiment of the present invention and an air conditioner 20 equipped with the same. The air conditioner 20 is a ceiling-mounted cassette indoor unit. The air conditioner 20 comprises a substantially rectangular parallelepiped casing 21 that is mounted in an opening in a ceiling 30 inside the room, and a decorative panel 22 attached to the bottom of the casing 21. The decorative panel 22 has a rectangular intake grille 23 and a plurality of air outlets 24 provided along each side of the intake grille 23. An angle-adjustable air deflector 25 is arranged at the air outlet 24.

[0010] An inner wall 26 is attached to the casing 21, covering the inner side and peripheral edges of the top surface. A drain pan 27 is attached inside the casing 21 above the decorative panel 22, and a heat exchanger 28 is attached above the drain pan 27. In Fig. 1, reference numeral 29 denotes an air filter.

[0011] A fan motor 10 is attached to the center of the top surface of the casing 21. In the following description, the direction of the rotation axis of the motor shaft 11 of the fan motor 10 is referred to as the "axial direction," and the direction perpendicular to the axial direction is referred to as the "radial direction." The direction of rotation around the motor shaft 11 as the centerline is referred to as the "circumferential direction." Furthermore, terms indicating directions such as "up" and "down" are based on the directions in Figure 1.

[0012] A bell mouth 13 is attached to the drain pan 27. The bell mouth 13 is ring-shaped in a plan view from the axial direction, and has a generally arc-shaped cross section with an inner diameter that decreases toward the fan motor 10 (upward). Although the bell mouth 13 has a generally arc-shaped cross section, it includes a cylindrical surface 13A that is generally parallel to the axial direction on the inner side in the radial direction (upper axial side) that is perpendicular to the rotation axis. A turbofan 100, which will be described below, is disposed so as to face the bell mouth 13 in the axial direction.

[0013] 2. Turbofan configuration The turbofan 100 comprises a hub 120, a shroud 130, and a plurality of blades 140. The motor shaft 11 of the fan motor 10 is attached to the hub 120. As shown in FIG. 2 , the hub 120 comprises a ring-shaped top plate 121, an inclined plate 122 that slopes downward from the inner peripheral edge of the top plate 121 toward the center, and a bottom plate 123 that is disposed on the lower edge of the inclined plate 122.

[0014] A hole 124 is formed in the center of the bottom plate 123, and a screw (not shown) formed on the tip of the motor shaft 11 of the fan motor 10 is inserted into the hole 124. The hub 120 is attached to the motor shaft 11 by threading a nut 12 onto the screw.

[0015] A shroud 130 is disposed radially outwardly of the upper end of the bell mouth 13 so as to face the bell mouth 13. A plurality of blades 140 are disposed at equal intervals in the circumferential direction between the shroud 130 and the hub 120. This connects the shroud 130 to the hub 120 and causes the shroud 130 to rotate together with the hub 120.

[0016] 3 to 5, the shroud 130 has an opposing surface (top wall 135) formed around the entire periphery on the outer periphery in the radial direction perpendicular to the axial direction, which faces the hub 120. Specifically, the shroud 130 includes a bottom wall 131 extending radially and perpendicular to the axial direction, an inner circumferential wall 132 extending axially upward from a radially inner edge of the bottom wall 131 and generally parallel to the axial direction, and an outer circumferential wall 133 extending axially upward from a radially outer edge of the bottom wall 131 and generally parallel to the axial direction. The bottom wall 131 connects the inner circumferential wall 132 and the outer circumferential wall 133.

[0017] The outer peripheral wall 133 is taller in the axial direction than the inner peripheral wall 132, and has an inclined wall 134 that slopes upward from its upper axial edge toward the radially outward direction, and a top wall 135 that extends radially outward from the radially outer edge of the inclined wall 134 and is generally perpendicular to the axial direction. The top wall 135 is an opposing surface that faces the hub 120 on the radially outer side of the shroud 130, perpendicular to the axial direction. A gently sloping portion 134a that slopes more gently toward the radially outward direction is formed in the radially outer portion of the inclined wall 134.

[0018] The shroud 130 is disposed so that the inner circumferential surface of its inner circumferential wall 132 overlaps a portion of the bell mouth 13 with a gap therebetween in the radial direction. The inner circumferential wall 132 has a surface that is approximately parallel to the cylindrical surface 13A of the bell mouth 13. Furthermore, the axially upper end 132c of the inner circumferential wall 132 is located higher than the axially upper end 13B of the bell mouth 13. In other words, the hub 120-side end 132c of the inner circumferential wall 132 is closer to the hub 120 in the axial direction than the hub 120-side end 13B of the bell mouth 13. Furthermore, a corner 132a of the inner circumferential wall 132 facing radially outward is chamfered to have an arc-shaped cross section. A groove 136 is formed by the bottom wall 131, the inner circumferential wall 132, and the outer circumferential wall 133. The groove 136 is formed so as to be recessed in the axial direction on the surface facing the hub 120. The groove 136 is formed around the entire inner periphery of the shroud 130 .

[0019] The bottom wall 131 of the groove 136 is located below (upstream of) the axially upper end 13B of the bell mouth 13 shown in Fig. 1. A plurality of blades 140 are installed at equal intervals in the circumferential direction between the hub 120 and the shroud 130. Furthermore, when the blades 140 and the grooves 136 are projected onto an imaginary plane perpendicular to the rotation axis, the blades 140 are arranged so that a portion of each blade 140 overlaps with the corresponding groove 136.

[0020] The blade 140 includes an outer blade 141 fixed to the inclined wall 134 and the top wall 135 of the shroud 130, and an inner blade 142 having a contour that forms a convex curve that is convex radially inward in a side view and reaches the hub 120. The outer blade 141 and the inner blade 142 are fixed to the top plate 121 of the hub 120. In the cross section of the blade 140 shown in Figure 4, the outer blade 141 is located from the center of the blade 140 to the outer periphery, and the inner blade 142 is located from the center of the blade 140 to the inner periphery.

[0021] Blade 140 is a swept-back blade, and outer blade 141 is inclined in the direction opposite to the direction of rotation indicated by arrow R in Figure 4. In addition, inner blade 142 is inclined in the direction of rotation relative to outer blade 141, and blade 140 as a whole has a shape recessed in the direction opposite to the direction of rotation.

[0022] 3. Function of air conditioners When the fan motor 10 rotates, the turbofan 100 rotates, and air is drawn into the air conditioner 20 through the intake grille 23 by the action of the blades 140. The speed of the drawn air is increased as it passes through the bell mouth 13, and the air is deflected radially outward by the action of the shroud 130 and blown out toward the heat exchanger 28. The air that has passed through the heat exchanger 28 is blown out from the air outlet 24 into the room.

[0023] 4. Turbofan function The airflow that has passed through the bellmouth 13 flows into the groove 136 and generates tiny separation vortices in the upper (downstream) portion of the groove 136, which draws the airflow toward the shroud 130, increasing the airflow speed on the shroud 130 side and making the airflow speed distribution uniform. Therefore, in an air conditioner 20 equipped with such a turbofan 100, the heat exchange capacity can be improved.

[0024] In particular, in an air conditioner 20 equipped with a turbofan 100 having the above configuration, the axially upper end 132c of the inner circumferential wall 132 is located higher than the axially upper end 13B of the bell mouth 13, so the airflow is blocked by the inner circumferential wall 132 and tends to flow around into the groove 136, making it easier for separation vortices to occur. In addition, the corners 132a of the inner circumferential wall 132 facing radially outward are chamfered to have an arc-shaped cross section, making it easier for the airflow to flow into the groove 136.

[0025] [2] Second embodiment 1. Turbofan configuration A turbofan (centrifugal fan) 101 according to a second embodiment of the present invention will be described with reference to Figures 6 to 11. In the following description, the same components as those in the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted.

[0026] As shown in Figures 8 to 11, the shroud 200 in the turbofan 101 of the second embodiment also includes a bottom wall 210 extending radially and perpendicular to the axial direction, an inner wall 220 extending axially upward from the radially inner edge of the bottom wall 210 and approximately parallel to the axial direction, and an outer wall 230 extending axially upward from the radially outer edge of the bottom wall 210 and approximately parallel to the axial direction.

[0027] An end 231 of the outer peripheral wall 230 is at approximately the same height in the axial direction as an end 222 of the inner peripheral wall 220, and an inclined wall 240 is formed from its upper axial edge portion with an upward slope radially outward, and a top wall 250 is formed extending radially outward from the radially outer edge portion of the inclined wall 240 and substantially perpendicular to the axial direction. The top wall 250 is an opposing surface that faces the hub 120 on the radially outer side of the shroud 200 in the direction perpendicular to the axial direction.

[0028] The axially upper end 222 of the inner circumferential wall 220 is located above the axially upper end 13B of the bell mouth 13. In other words, the hub 120-side end 222 of the inner circumferential wall 220 is closer to the hub 120 in the axial direction than the hub 120-side end 13B of the bell mouth 13 shown in FIG. 1 . Furthermore, a groove 260 is formed by the bottom wall 210, the inner circumferential wall 220, and the outer circumferential wall 230, and a partition wall 270 is formed in the radial center of the groove 260, extending axially upward and having a surface substantially parallel to the axial direction. The hub 120-side end 273 of the partition wall 270 is formed so that the axial distance from the hub 120 is shorter than that of the hub 120-side end 222 of the inner circumferential wall 220. The partition wall 270 is provided between the inner circumferential wall 220 and the outer circumferential wall 230, and one end is connected to the bottom wall 210, with a surface substantially parallel to the rotation axis.

[0029] The groove 260 is divided by a partition wall 270 into an inner circumferential groove 261 on the inner circumferential side and an outer circumferential groove 262 on the outer circumferential side, and the outer circumferential groove 262 is located axially higher than the inner circumferential groove 261. In other words, the bottom of the inner circumferential groove 261 is located lower (upstream) than the end 13B of the bell mouth 13 on the hub 120 side. Furthermore, the position of an end 273 of the partition wall 270 on the hub 120 side is higher than the top wall 250. The end 273 of the partition wall 270 on the hub 120 side is closer to the hub 120 in the axial direction than the outer circumferential wall 250.

[0030] A plurality of protrusions 221 that protrude axially upward are formed at equal intervals in the circumferential direction on an end 222 of the inner circumferential wall 220 facing the hub 120. This gives the end 222 of the inner circumferential wall 220 facing the hub 120 an uneven shape along the circumferential direction. Meanwhile, a plurality of recesses 271 that are recessed axially downward are formed at equal intervals in the circumferential direction on an end 273 of the partition wall 270 facing the hub 120. This gives the end 273 of the partition wall 270 facing the hub 120 an uneven shape along the circumferential direction.

[0031] In the groove 260, flat ribs 280 extending in a radial direction (radially) with respect to the center line of the shroud 200 are formed at equal intervals in the circumferential direction, and recesses 271 are arranged between the ribs 280. The ribs 280 are connected to the inner circumferential wall 220, the outer circumferential wall 230, and the bottom wall 210, respectively. Note that the ribs 280 may extend in a direction deviated from the radial direction with respect to the center line of the shroud 200.

[0032] 11 , the rib 280 is made up of an inner circumferential rib 281 that is generally trapezoidal in side view and is provided from the upper end 222 of the inner circumferential wall 220 to the axial position of the recess 271 of the partition wall 270, defining the inner circumferential groove, and an outer circumferential rib 282 that is generally rectangular in side view and is provided from the partition wall 270 to the inclined wall 240 on the outer circumferential side, defining the outer circumferential groove 262. The outer circumferential rib 282 extends in the axial direction above the partition wall 270.

[0033] The blades 150 face the shroud 200 configured as described above. As shown in Fig. 9, the blades 150 include an outer blade 151 fixed to the inclined wall 240 and the top wall 250 of the shroud 200, and an inner blade 152 having a contour that forms a convex curve that is convex radially inward in a side view and reaches the hub 120. The outer blade 151 and the inner blade 152 are fixed to the top plate 121 of the hub 120. In the cross section of the blade 150 shown in Fig. 10, the outer blade 151 extends from the center of the blade 150 to the outer periphery, and the inner blade 152 extends from the center of the blade 150 to the inner periphery.

[0034] The blade 150 has a notch 153 that is generally rectangular in side view and extends from the inner peripheral edge of the outer blade 151 to the inner peripheral blade 152, and the notch 153 straddles the recess 271 of the partition wall 270. As a result, the blade 150 is not present in the inner peripheral groove 261 or the outer peripheral groove 262. In other words, the blade 150 is not disposed in the space within the groove formed by the inner peripheral groove 261 and the outer peripheral groove 262.

[0035] Blade 150 is a swept-back blade, and outer blade 151 is inclined in the direction opposite to the direction of rotation indicated by arrow R in Figure 7. In addition, inner blade 152 is inclined in the direction of rotation relative to outer blade 151, and blade 150 as a whole has a shape recessed in the direction opposite to the direction of rotation.

[0036] 2. Turbofan function The airflow that has passed through the bellmouth 13 flows into the inner circumferential groove 261 and the outer circumferential groove 262, and tiny separation vortices are generated in the downstream portions of the inner circumferential groove 261 and the outer circumferential groove 262. This draws the airflow toward the shroud 200, increasing the airflow speed on the shroud 200 side and making it possible to uniformize the airflow speed distribution. Therefore, the heat exchange capacity of the air conditioner 20 equipped with the turbofan 101 can be improved.

[0037] In particular, in the second embodiment described above, the edge of the inner circumferential wall 220 on the hub 120 side is formed with protrusions 221 along the circumferential direction to form an uneven shape, and therefore, by adjusting the height and circumferential length of the protrusions 221, the amount of airflow blocked by the inner circumferential wall 220 can be adjusted.

[0038] Furthermore, in the second embodiment, the partition wall 270 having a surface substantially parallel to the axial direction is provided between the inner circumferential wall 220 and the outer circumferential wall 230, so that the airflow blocked by the inner circumferential wall 220 turns around to the inner circumferential groove 261 side, generating a separation vortex, and the airflow blocked by the partition wall 270 turns around to the outer circumferential groove 262 side, generating a separation vortex. In this way, because separation vortices are generated at two locations, the inner circumferential groove 261 and the outer circumferential groove 262, the airflow is drawn toward the shroud 200 side, and the wind speed on the shroud 200 side increases.

[0039] Since the end 273 of the partition wall 270 on the hub 120 side is closer to the hub 120 in the axial direction than the end 222 of the inner wall 220 on the hub 120 side, the airflow is reliably blocked by the partition wall 270, making it easier for it to flow around the outer circumferential groove 262, and further making it easier for separation vortices to occur.

[0040] In addition, the partition wall 270 has an uneven shape along the circumferential direction at the edge on the hub 120 side due to the recess 271, so by adjusting the depth and circumferential length of the recess 271, the amount of airflow blocked by the partition wall 270 can be adjusted.

[0041] In the second embodiment, since there are no blades 150 in the inner circumferential groove 261 and the outer circumferential groove 262, the separation vortex generated in the downstream portion of the inner circumferential groove 261 and the outer circumferential groove 262 is not disturbed by the airflow generated by the blades 150.

[0042] In the second embodiment, ribs 280 are provided connected to the inner circumferential wall 220, the outer circumferential wall 230, and the bottom wall 210, respectively, so that the separation vortex generated between the ribs 280 is carried in the rotational direction of the shroud 200, making it difficult for the separation vortex to become turbulent.

[0043] In the second embodiment, the outer circumferential groove 262 is disposed closer to the hub 120 than the inner circumferential groove 261, so that the airflow flowing downstream on the outer circumferential side easily flows into the outer circumferential groove 262, making it easier for separation vortices to occur.

[0044] 3. Example of changes The present invention is not limited to the first and second embodiments described above, and various modifications are possible as follows. i) In the first and second embodiments, the present invention is applied to a turbofan, but it can also be applied to a sirocco fan with forward-curved blades and a radial fan with radial blades.

[0045] ii) The shroud 200 of the second embodiment can be used in place of the shroud 130 of the first embodiment. iii) A plurality of partition walls 270 can be provided in the groove 260 in a concentric circle arrangement. iv) The top walls 135, 250 may be tapered downwardly in the radially outward direction. [Explanation of symbols]

[0046] 10... Fan motor, 11... Motor shaft, 12... Nut, 13... Bell mouth, 13A... Cylindrical surface, 13B... End, 20... Air conditioner, 21... Casing, 22... Decorative panel, 23... Intake grille, 24... Outlet, 25... Air deflector, 26... Inner wall, 27... Drain pan, 28... Heat exchanger, 29... Air filter, 30... Ceiling, 100, 101... Turbo fan (centrifugal fan), 120... Hub, 121... Top plate, 122... Inclined plate, 123... Bottom plate, 124... Hole, 130, 200 ...Shroud, 131,210...bottom wall, 132,220...inner peripheral wall, 132a...corner portion, 132c...end portion, 133,230...outer peripheral wall, 134,240...inclined wall, 134a...gently inclined portion, 135,250...top wall, 136,260...groove, 140,150...wing, 141,151...outer peripheral blade, 142,152...inner peripheral blade, 153...notch, 222,231,273...end portion, 261...inner peripheral groove, 262...outer peripheral groove, 270...partition wall, 280...rib, 281...inner peripheral rib, 282...outer peripheral rib.

Claims

1. a hub to which a motor shaft serving as a rotation axis is fixed at the center; an annular shroud disposed opposite the hub; and a plurality of blades connecting the shroud and the hub to each other, the shroud has a groove recessed in the rotation axis direction on a surface facing the hub, A centrifugal fan, wherein the groove is formed around the entire inner periphery of the shroud.

2. The groove is an inner circumferential wall that is substantially parallel to the rotation axis when viewed in a direction perpendicular to the cross section along the rotation axis; an outer circumferential wall disposed radially outward of the inner circumferential wall and substantially parallel to the rotation shaft; The centrifugal fan according to claim 1 , further comprising: a bottom wall connecting the inner circumferential wall and the outer circumferential wall.

3. The centrifugal fan according to claim 2 , wherein the inner peripheral wall has an end surface on the hub side that has an uneven shape along a circumferential direction with the rotation shaft as a center line.

4. 3. The centrifugal fan according to claim 2, further comprising a partition wall disposed between said inner peripheral wall and said outer peripheral wall, said partition wall having one end connected to said bottom wall and a surface substantially parallel to said rotation shaft.

5. 5. The centrifugal fan according to claim 4, wherein the end of the partition wall on the hub side is closer to the hub in the direction of the rotation axis than the end of the inner circumferential wall on the hub side.

6. the shroud has an opposing surface formed around the entire periphery on the outer side in a radial direction perpendicular to the rotation axis, the opposing surface facing the hub; 6. The centrifugal fan according to claim 4, wherein a distance between the hub and an end of the partition wall on the hub side is shorter in the direction of the rotation axis than an outer peripheral end of the shroud.

7. The centrifugal fan according to claim 5 , wherein the partition wall has an end surface on the hub side that has an uneven shape along a circumferential direction about the rotation shaft.

8. The centrifugal fan according to claim 1 or 2, wherein the blades are not disposed in the space within the groove.

9. 3. The centrifugal fan according to claim 2, wherein flat ribs are provided on the inner peripheral wall, the outer peripheral wall, and the bottom wall, respectively.

10. A centrifugal fan comprising: the centrifugal fan according to claim 1; and a bell mouth; An air conditioner in which a portion of the bell mouth is arranged inside the inner circumferential surface of the shroud so as to overlap with the inner circumferential surface of the shroud with a gap therebetween.

11. the bell mouth has a cylindrical surface that is substantially parallel to the rotation axis on the inner side in a radial direction perpendicular to the rotation axis, The groove is an inner circumferential wall having a surface substantially parallel to the cylindrical surface of the bell mouth; an outer circumferential wall disposed radially outward of the inner circumferential wall and having a surface substantially parallel to the rotation axis; The air conditioner according to claim 10, further comprising: a bottom wall connecting the inner peripheral wall and the outer peripheral wall.

12. The air conditioner according to claim 11, wherein the hub-side end of the inner circumferential wall is closer to the hub in the direction of the rotation axis than the hub-side end of the bell mouth.

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