Centrifugal fan and air conditioner equipped therewith

Abstract

We provide a centrifugal fan that can equalize the wind speed distribution of the blown airflow. [Solution] The turbofan comprises a hub 120 to which a motor shaft serving as the axis of rotation is fixed in the center, an annular shroud 130 positioned opposite the hub 120, and a plurality of blades 140 connecting the shroud 130 and the hub 120 to each other. The shroud 130 has a groove 136 recessed in the direction of the axis of rotation on the surface facing the hub 120, and the groove 136 is formed around the entire circumference on the inner side 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 Art

[0002] The centrifugal fan mounted in the indoor unit of an air conditioner generates a flow of air in the ventilation path connecting the suction port and the blowout port of the indoor unit by rotating. In a centrifugal fan, generally, a shroud is arranged adjacent to a bell mouth (see, for example, Patent Document 1). According to Patent Document 1, the shroud has a cross-sectional arc shape, and has the function of bending the air sucked into the centrifugal fan and flowing in the direction of the rotation axis of the motor in the centrifugal direction (outer peripheral side) and sending the air flow to the heat exchanger arranged around the centrifugal fan. Further, by reducing the gap between the shroud and the bell mouth, there is also an effect of suppressing the backflow of the air blown out from the centrifugal fan through the gap and improving the blowing efficiency.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the cross-sectional arc-shaped shroud in the centrifugal fan disclosed in Patent Document 1, since the effect of bending the air flow to the outer peripheral side is small, the air flow is biased toward the hub side facing the shroud. For this reason, a non-uniform wind speed distribution occurs in which the wind speed on the hub side is large and the wind speed on the shroud side is small. As a result, variations in the wind speed occur in the air flow passing through the heat exchanger, the ventilation resistance increases at the location where the air flow with a large wind speed passes through the heat exchanger, and the heat exchange performance decreases at the location where the air flow with a small wind speed passes through.

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

[0006] The present invention relates to a centrifugal fan comprising a hub to which a motor shaft serving as a rotation axis is fixed at the center, an annular shroud positioned opposite the hub, and a plurality of blades connecting each other between 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 circumference on the inner side of the shroud. [Effects of the Invention]

[0007] According to the present invention, the wind speed distribution of the airflow blown out from a 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 that air conditioner can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view showing an air conditioner equipped with a turbo fan according to a first embodiment of the present invention. [Figure 2] This is a perspective view showing a turbofan according to the first embodiment of the present invention. [Figure 3] This is a perspective view showing a cross-section of a portion of the turbofan of the first embodiment. [Figure 4] This is a cross-sectional view taken along line IV-IV in Figure 5. [Figure 5] (A) is a perspective view showing a cross-section of a part of the turbo fan of the first embodiment, and (B) is an enlarged view of the part indicated by arrow B in (A). [Figure 6] This is a perspective view showing a turbofan according to a second embodiment of the present invention. [Figure 7] This is a perspective view of the turbofan of the second embodiment, cut along line XX in Figure 9, showing the shroud. [Figure 8]This is a perspective view showing a cross-section of a portion of the turbofan of the second embodiment. [Figure 9] (A) is a perspective view showing a cross-section of a part of the turbo fan of the second embodiment, and (B) is an enlarged view of the part indicated by arrow B in (A). [Figure 10] This is a cross-sectional view along line XX in Figure 9. [Figure 11] This is a perspective view showing a cross-section of a portion of the turbofan of the second embodiment. [Modes for carrying out the invention]

[0009] [1] First Embodiment 1. Air Conditioner Configuration Figure 1 is a longitudinal cross-sectional view showing the configuration of a turbo fan (centrifugal fan) 100 and an air conditioner 20 equipped therewith according to a first embodiment of the present invention. This air conditioner 20 is a ceiling-mounted cassette indoor unit. This air conditioner 20 comprises a substantially rectangular parallelepiped casing 21 embedded in an opening provided in the ceiling 30 of a room, and a decorative panel 22 attached to the lower part 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 adjustable air deflector 25 is provided at each air outlet 24.

[0010] The casing 21 is fitted with an inner wall 26 that covers the inner surface and the periphery of the top surface. Inside the casing 21, a drain pan 27 is fitted above the decorative panel 22, and a heat exchanger 28 is fitted above the drain pan 27. In Figure 1, reference numeral 29 denotes an air filter.

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

[0012] A bell mouth 13 is attached to the drain pan 27. The bell mouth 13 is ring-shaped in plan view as viewed from the axial direction, and has a substantially arc-shaped cross section with a decreasing inner diameter as it goes toward the fan motor 10 side (upper side). The bell mouth 13 includes a cylindrical surface 13A that is substantially parallel to the axial direction on the inner side in the radial direction (upper side in the axial direction) that is orthogonal to the rotation axis although it has a substantially arc-shaped cross section. And a turbo fan 100 described below is arranged so as to face the bell mouth 13 in the axial direction.

[0013] 2. Structure of Turbo Fan The turbo fan 100 is composed of 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 includes 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 arranged at the lower edge of the inclined plate 122.

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

[0015] The shroud 130 is arranged so as to face the outer side in the radial direction of the upper end portion of the bell mouth 13. A plurality of blades 140 are installed at equal intervals in the circumferential direction between the shroud 130 and the hub 120. Thereby, the shroud 130 is coupled to the hub 120 and rotates together with the hub 120.

[0016] As shown in FIGS. 3 to 5, on the outer peripheral side in the radial direction orthogonal to the axial direction, a facing surface (top wall 135) facing the hub 120 is formed over the entire circumference on the shroud 130. Specifically, the shroud 130 includes a bottom wall 131 extending in the radial direction and orthogonal to the axial direction, an inner peripheral wall 132 extending axially upward from the edge portion on the radially inner side of the bottom wall 131 and substantially parallel to the axial direction, and an outer peripheral wall 133 extending axially upward from the edge portion on the radially outer side of the bottom wall 131 and substantially parallel to the axial direction. The bottom wall 131 connects the inner peripheral wall 132 and the outer peripheral wall 133.

[0017] The outer peripheral wall 133 is higher in the axial direction than the inner peripheral wall 132, and an inclined wall 134 having an upward gradient is formed from the edge portion on the upper side in the axial direction toward the radially outer side. A top wall 135 extending radially outward from the edge portion on the radially outer side of the inclined wall 134 and substantially orthogonal to the axial direction is formed. The top wall 135 is a facing surface that faces the hub 120 on the outer side in the radial direction orthogonal to the axial direction in the shroud 130. A gently inclined portion 134a with a gentler inclination toward the radially outer side is formed in the radially outer portion of the inclined wall 134.

[0018] The shroud 130 is arranged such that the inner peripheral surface of its inner peripheral wall 132 overlaps radially with a part of the bellmouth 13 with a gap. The inner peripheral wall 132 has a surface substantially parallel to the cylindrical surface 13A of the bellmouth 13. Also, the upper end portion 132c in the axial direction of the inner peripheral wall 132 is located above the upper end portion 13B in the axial direction of the bellmouth 13. In other words, the end portion 132c on the hub 120 side of the inner peripheral wall 132 is shorter in the axial direction from the hub 120 than the end portion 13B on the hub 120 side of the bellmouth 13. Also, a chamfer with an arcuate cross section is formed at the corner portion 132a facing the radially outer side of the inner peripheral wall 132. And a groove 136 is formed by the bottom wall 131, the inner peripheral wall 132, and the outer peripheral wall 133. The groove 136 is formed to be recessed axially on the surface facing the hub 120. Also, the groove 136 is formed over the entire circumference on the inner peripheral side of the shroud 130.

[0019] The bottom wall 131 of the groove 136 is located below (upstream of) the axial upper end 13B of the bell mouth 13 shown in Figure 1. Multiple wings 140 are arranged between the hub 120 and the shroud 130 at equal intervals in the circumferential direction. Furthermore, when the wings 140 and the groove 136 are projected onto a virtual plane perpendicular to the axis of rotation, a portion of the wings 140 and the groove 136 overlap.

[0020] The wing 140 comprises an outer wing 141 fixed to the inclined wall 134 and top wall 135 of the shroud 130, and an inner wing 142 having a contour that extends to the hub 120, drawing a convex curve that is radially convex inward when viewed from the side. The outer wing 141 and the inner wing 142 are fixed to the top plate 121 of the hub 120. In the cross-section of the wing 140 shown in Figure 4, the outer wing 141 is defined as the part of the wing 140 from the center outward, and the inner wing 142 is defined as the part of the wing 140 from the center inward.

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

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

[0023] 4. The function of the turbo fan The airflow that has passed through the bell mouth 13 flows into the groove 136, where a small separation vortex is generated in the upper (downstream) part of the groove 136. This draws the airflow towards the shroud 130, increasing the airflow velocity on the shroud 130 side and homogenizing the airflow velocity distribution. Therefore, an air conditioner 20 equipped with such a turbo fan 100 can improve its heat exchange capacity.

[0024] In particular, in the air conditioner 20 equipped with the turbo fan 100 as described above, the axial upper end 132c of the inner circumferential wall 132 is located above the axial upper end 13B of the bell mouth 13, so the airflow is easily blocked by the inner circumferential wall 132 and tends to flow around into the groove 136, making it easier for separation vortices to form. In addition, a chamfer with an arc shape in cross-section is formed on the radially outward-facing corner portion 132a of the inner circumferential wall 132, which makes it easier for the airflow to flow into the groove 136.

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

[0026] In the turbo fan 101 of the second embodiment, as shown in Figures 8 to 11, the shroud 200 also includes a bottom wall 210 that extends radially and is perpendicular to the axial direction, an inner circumferential wall 220 that extends axially upward from the radially inner edge of the bottom wall 210 and is substantially parallel to the axial direction, and an outer circumferential wall 230 that extends axially upward from the radially outer edge of the bottom wall 210 and is substantially parallel to the axial direction.

[0027] The end 231 of the outer peripheral wall 230 is at approximately the same axial height as the end 222 of the inner peripheral wall 220, and an inclined wall 240 is formed from its axially upper edge toward the radially outward direction, and a top wall 250 is formed extending radially outward from the radially outward edge of the inclined wall 240 and substantially perpendicular to the axial direction. The top wall 250 is the opposing surface of the shroud 200 that faces the hub 120 on the radially outward side 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 shorter in the axial direction from the hub 120 than the hub 120-side end 13B of the bell mouth 13 shown in Figure 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 it is shorter in the axial direction from the hub 120 than 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, with one end connected to the bottom wall 210 and having a surface substantially parallel to the axis of rotation.

[0029] The groove 260 is divided by the partition wall 270 into an inner groove 261 on the inner circumference side and an outer groove 262 on the outer circumference side, with the outer groove 262 located axially above the inner groove 261. That is, the bottom of the inner groove 261 is located below (upstream of) the hub 120 side end 13B of the bell mouth 13. Also, the hub 120 side end 273 of the partition wall 270 is located above the top wall 250. The hub 120 side end 273 of the partition wall 270 is shorter axially from the hub 120 than the outer wall 250.

[0030] Multiple protrusions 221 projecting upward in the axial direction are formed at equal intervals in the circumferential direction on the end 222 of the inner circumferential wall 220 on the hub 120 side. As a result, the end 222 of the inner circumferential wall 220 on the hub 120 side has an uneven shape along the circumferential direction. On the other hand, multiple recesses 271 recessing downward in the axial direction are formed at equal intervals in the circumferential direction on the end 273 of the partition wall 270 on the hub 120 side. As a result, the end 273 of the partition wall 270 on the hub 120 side has an uneven shape along the circumferential direction.

[0031] Flat, plate-shaped ribs 280 are formed in the groove 260 at equal intervals in the circumferential direction, extending radially (radially) with respect to the centerline of the shroud 200, 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. The ribs 280 may also extend in a direction offset from the radial direction with respect to the centerline of the shroud 200.

[0032] As shown in Figure 11, the rib 280 consists of an inner circumferential rib 281, which 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 and has a substantially trapezoidal shape in side view that defines the inner circumferential groove, and an outer circumferential rib 282, which is provided from the partition wall 270 to the outer inclined wall 240 and has a substantially rectangular shape in side view that defines the outer circumferential groove 262. The outer circumferential rib 282 extends in the axial direction to a range above the partition wall 270.

[0033] The shroud 200 with the above configuration has a wing 150 facing it. As shown in Figure 9, the wing 150 comprises an outer wing 151 fixed to the inclined wall 240 and top wall 250 of the shroud 200, and an inner wing 152 having a contour that is convex inward in the radial direction when viewed from the side and extends to the hub 120. The outer wing 151 and the inner wing 152 are fixed to the top plate 121 of the hub 120. In the cross-section of the wing 150 shown in Figure 10, the outer wing 151 is defined as the part of the wing 150 from the center to the outer circumference, and the inner wing 152 is defined as the part of the wing 150 from the center to the inner circumference.

[0034] The wing 150 has a roughly rectangular notch 153 formed in a side view, extending from the inner side edge of the outer wing 151 to the inner wing 152, and the notch 153 straddles the recess 271 of the partition wall 270. As a result, the wing 150 is not present in the inner groove 261 and the outer groove 262. In other words, the wing 150 is not positioned in the space within the grooves formed by the inner groove 261 and the outer groove 262.

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

[0036] 2. The function of the turbo fan The airflow that has passed through the bell mouth 13 flows into the inner groove 261 and the outer groove 262, generating minute separation vortices in the downstream portions of the inner groove 261 and the outer groove 262. This draws the airflow towards the shroud 200, increasing the airflow velocity on the shroud 200 side and homogenizing the airflow velocity distribution. Therefore, the air conditioner 20 equipped with the turbo fan 101 can improve its heat exchange capacity.

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

[0038] Furthermore, in the second embodiment described above, a 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. As a result, the airflow blocked by the inner circumferential wall 220 curves around to the inner circumferential groove 261 side, generating a separation vortex, and the airflow blocked by the partition wall 270 curves around to the outer circumferential groove 262 side, generating another separation vortex. Thus, since separation vortices are generated at two locations, the inner circumferential groove 261 and the outer circumferential groove 262, the airflow is drawn towards the shroud 200 side, and the wind speed on the shroud 200 side becomes greater.

[0039] The end 273 of the partition wall 270 on the hub 120 side is shorter in the axial direction from the hub 120 than the end 222 of the inner circumferential wall 220 on the hub 120 side. As a result, the airflow is reliably blocked by the partition wall 270 and more likely to flow around into the outer circumferential groove 262, further increasing the likelihood of separation vortices being generated.

[0040] Furthermore, since the partition wall 270 has an uneven shape along the circumferential direction at its edge on the hub 120 side due to the recess 271, the amount of airflow blocked by the partition wall 270 can be adjusted by adjusting the depth and circumferential length of the recess 221.

[0041] In the second embodiment described above, since there are no blades 150 in the inner groove 261 and the outer groove 262, the separation vortices generated in the downstream portions of the inner groove 261 and the outer groove 262 are not disturbed by the airflow generated by the blades 150.

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

[0043] In the second embodiment described above, since the outer circumferential groove 262 is positioned closer to the hub 120 than the inner circumferential groove 261, airflow flowing downstream on the outer circumference is more likely to flow into the outer circumferential groove 262, making it easier for separation vortices to form.

[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) Although the first and second embodiments described above apply the present invention to a turbo fan, it can also be applied to a sirocco fan having forward-facing blades and a radial fan having radially oriented blades.

[0045] ii) The shroud 200 of the second embodiment can be used instead of the shroud 130 of the first embodiment. iii) Multiple partition walls 270 can be provided in the groove 260 in a concentric circular pattern. iv) The top wall 135,250 can be inclined to have a downward slope toward 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 circumferential wall, 132a...Corner, 132c...End, 133,230...Outer circumferential wall, 134,240...Inclined wall, 134a...Sloping section, 135,250...Top wall, 136,260...Groove, 140,150...Wing, 141,151...Outer circumferential wing, 142,152...Inner circumferential wing, 153...Notch, 222,231,273...End, 261...Inner circumferential groove, 262...Outer circumferential groove, 270...Partition wall, 280...Rib, 281...Inner circumferential rib, 282...Outer circumferential rib.

Claims

1. It comprises a hub to which a motor shaft serving as the axis of rotation is fixed at the center, an annular shroud positioned opposite the hub, and a plurality of wings connecting the shroud and the hub to each other, The shroud has a groove on the surface facing the hub that is recessed in the direction of the rotation axis, The groove is formed around the entire circumference on the inner side of the shroud, forming a centrifugal fan.

2. The groove is In the cross-section along the rotation axis, when viewed from a direction perpendicular to the cross-section, the inner circumferential wall is substantially parallel to the rotation axis, An outer peripheral wall is positioned radially outward from the inner peripheral wall and is substantially parallel to the axis of rotation, A 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 circumferential wall has an uneven shape along the circumferential direction with respect to the rotation axis as the center line at the end face on the hub side.

4. The centrifugal fan according to claim 2, wherein a partition wall is provided between the inner circumferential wall and the outer circumferential wall, one end of which is connected to the bottom wall and which has a surface substantially parallel to the rotation axis.

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

6. The shroud has an opposing surface formed around its entire circumference that faces the hub on the radially outer side perpendicular to the axis of rotation, The centrifugal fan according to claim 4 or 5, wherein the hub-side end of the partition wall is shorter in the direction of rotation axis from the hub than the outer peripheral end of the shroud.

7. The centrifugal fan according to claim 5, wherein the partition wall has an uneven shape along the circumferential direction centered on the rotation axis at the end face on the hub side.

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

9. The centrifugal fan according to claim 2, wherein flat plate-shaped ribs are provided connected to the inner circumferential wall, the outer circumferential wall, and the bottom wall, respectively.

10. The invention comprises a centrifugal fan as described in claim 1 and a bell mouth, An air conditioner in which a portion of the bell mouth is positioned to overlap the inner surface of the shroud with a gap in between.

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

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

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