INDOOR UNIT FOR AIR-CONDITIONING DEVICE

Abstract

 Provided is an indoor unit (100) including: a main body (1) including an air inlet (2) and an air outlet (3); and a cross-flow fan (8) including an impeller (8a), in which the impeller includes a plurality of blades (8c), in which the blades each include a step (16) formed on a suction surface (13b) or a pressure surface (13a), in which the step is formed so that a fan inner peripheral-side part is further projected than a fan outer peripheral-side part, and in which the step is formed so as to extend obliquely with respect to a rotation axis of the impeller, to thereby vary in height over a direction of the rotation axis of the impeller.

Description

Technical Field

[0001] The present invention relates to an indoor unit for an air-conditioning apparatus.

Background Art

[0002] For example, in Patent Literature 1, there is proposed a cross-flow fan having a step recessed on a blade outer peripheral-side distal end portion side, which is formed at a blade outer peripheral-side end portion of a suction surface, in which a step leading edge portion or a step trailing edge portion of the step is extended obliquely with respect to the blade outer peripheral-side distal end portion.

[0003] Further, in Patent Literature 2, there is proposed a cross-flow fan having a sawtooth pattern formed on a blade surface of a blade, and a step formed at a position located at a predetermined distance from a blade edge along which the sawtooth pattern is formed.

[0004] Further, in Patent Literature 3, there is proposed a cross-flow fan in which, when a length of the blade in a longitudinal direction is divided into a plurality of regions, namely, first regions each adjacent to a support plate, a second region corresponding to a blade central portion, and third regions between the first regions and the second region, a blade outlet angle at the blade outer peripheral end portion in each of the regions becomes larger in the order of second region<first region<third region.

Citation List

Patent Literature

[0005] 

[PTL 1] JP 4840343 B2 (page 5, [0020], and FIGS. 4)

[PTL 2] JP 3995010 B2 (page 10, [0052], and FIG. 4)

[PTL 3] JP 4896213 B2 (page 6, [0024], and FIG. 7)

Summary of Invention

Technical Problem

[0006] However, in the cross-flow fan disclosed in Patent Literature 1, a height of the step is uniform in a fan rotation axis direction of the blade, and the height of the step is excessively large in a region where an air velocity is low relative to a difference in air velocity in the fan rotation axis direction. As a result, separation may occur in some regions to increase noise in a broad band.

[0007] Further, in the cross-flow fan disclosed in Patent Literature 2, when the height of the step is large, the separation may occur to increase the noise.

[0008] Still further, in the cross-flow fan disclosed in Patent Literature 3, on a fan air outlet side, the separation may occur due to the difference in air velocity. Further, on a fan air inlet side, the separation may occur because appropriate measures are not sufficiently taken against fluctuation to be caused by a variation in air velocity in each rotation of the fan.

[0009] The present invention has been made in view of the above, and it is an object of the present invention to provide an indoor unit for an air-conditioning apparatus capable of suppressing separation and reducing increase in noise.

Solution to Problem

[0010] In order to achieve the above-mentioned object, according to one embodiment of the present invention, there is provided an indoor unit for an air-conditioning apparatus, including: a main body including an air inlet and an air outlet; a cross-flow fan arranged inside the main body in a rotatable manner, the cross-flow fan including an impeller for causing air to be taken into the main body through the air inlet and causing the air to be blown out through the air outlet; and a stabilizer for partitioning a space inside the main body into an air inlet-side flow passage on an upstream side with respect to the cross-flow fan and an air outlet-side flow passage on a downstream side with respect to the cross-flow fan, in which the impeller includes a plurality of blades, in which the plurality of blades each include, in vertical sectional view, a step formed between an outer peripheral-side end portion and an inner peripheral-side end portion of the blades on at least one of a suction surface or a pressure surface being surfaces of the blades, in which the step is formed so that, on the surfaces, a fan inner peripheral-side part with respect to the step is further projected than a fan outer peripheral-side part with respect to the step, and in which the step is formed so as to extend obliquely with respect to a rotation axis of the impeller, and to vary in height over a direction of the rotation axis of the impeller.

[0011] Further, in the above-mentioned indoor unit for an air-conditioning apparatus, the step may include projections and recesses that are formed along the surfaces of the blades to be projected and recessed in a direction orthogonal to a longitudinal direction of each of the blades.

[0012] Further, in the above-mentioned indoor unit for an air-conditioning apparatus, the impeller may include a plurality of support plates, and the plurality of blades arranged between a corresponding pair of the support plates at intervals in a circumferential direction. The blades may each include at least a pair of first regions, a second region, and at least a pair of third regions as a plurality of regions that are different from each other in blade cross-section orthogonal to the rotation axis of the impeller. The first regions may be respectively parts that are adjacent to the support plates under a state in which the support plates are mounted to the impeller. The second region may be a part that is arranged between the corresponding pair of first regions. The third regions may be respectively arranged between the corresponding pair of first regions and between the second region and the corresponding first regions. A blade outlet angle of the first region, a blade outlet angle of the second region, and a blade outlet angle of the third region may be different from each other. The step may be formed in a boundary portion between an inner peripheral-side part in which three patterns of the first regions, the second region, and the third regions in the blade cross-section have the same shape, and an outer peripheral-side part in which the three patterns of the first regions, the second region, and the third regions in the blade cross-section have different shapes.

Advantageous Effects of Invention

[0013] According to the indoor unit for an air-conditioning apparatus of the one embodiment of the present invention, the separation can be suppressed and the increase in noise can be reduced.

Brief Description of Drawings

[0014] 

FIG. 1 is a view for illustrating an installation state of an air-conditioning apparatus according to a first embodiment of the present invention when viewed from an inside of a room.

FIG. 2 is a vertical sectional view for illustrating the air-conditioning apparatus of FIG. 1.

FIG. 3 is a view for illustrating front and lateral sides of an impeller of a cross-flow fan to be mounted to the air-conditioning apparatus of FIG. 1.

FIG. 4 is a sectional view taken along the line III-III in FIG. 3, for illustrating a blade of the impeller.

FIG. 5 is a sectional view taken along the line III-III in FIG. 3, for illustrating the blade of the impeller.

FIG. 6 is a sectional view taken along the line III-III in FIG. 3, for illustrating the blade of the impeller.

FIG. 7 is a perspective view of the blade of the impeller of FIG. 3 when viewed from a pressure surface side.

FIG. 8 is a view for illustrating a second embodiment of the present invention in the same manner as that of FIG. 7.

FIG. 9 is a view for illustrating a third embodiment of the present invention in the same manner as that of FIG. 7.

FIG. 10 is a view for illustrating a state of the blade of FIG. 9 when viewed along an extension direction of an outer peripheral-side end portion.

FIG. 11 is a view for illustrating a fourth embodiment of the present invention in the same manner as that of FIG. 3.

FIG. 12 is a view for illustrating cross-sections taken along the line A-A, the line B-B, and the line C-C in FIG. 11 in a superimposed manner.

FIG. 13 is a perspective view of a blade of an impeller of FIG. 11 when viewed from a pressure surface side.

Description of Embodiments

[0015] Now, embodiments of the present invention are described with reference to the accompanying drawings. Note that, in the drawings, the same reference symbols represent the same or corresponding parts.

First Embodiment

[0016] FIG. 1 is a view for illustrating an installation state of an air-conditioning apparatus according to a first embodiment of the present invention when viewed from an inside of a room. FIG. 2 is a vertical sectional view for illustrating the air-conditioning apparatus. FIG. 3 is a view for illustrating front and lateral sides of an impeller of a cross-flow fan to be mounted to the air-conditioning apparatus. Specifically, the part illustrated on the left side of the drawing sheet of FIG. 3 is a front view for illustrating the impeller, and the part illustrated on the right side of the drawing sheet of FIG. 3 is a side view for illustrating the impeller. Further, FIG. 4 to FIG. 6 are each a sectional view taken along the line III-III in FIG. 3, for illustrating a blade of the impeller. FIG. 7 is a perspective view of one of the blades of the impeller when viewed from a pressure surface side. Note that, in FIG. 4 to FIG. 6, hatching is omitted for the sake of clarity of illustration of an inside between blade surfaces.

[0017] In an indoor unit for the air-conditioning apparatus according to the first embodiment, the blades of the cross-flow fan to be mounted to the indoor unit are improved so as to be able to suppress noise and reduce electric power consumption of a fan motor.

[0018] A main body 1 serving as an outer shell of an indoor unit 100 includes a front panel 1a, a pair of lateral surfaces 1b, and an upper surface 1c. Note that, in the example illustrated in FIG. 1, the indoor unit 100 is an indoor unit of a wall hanging type to be installed to a wall 11a of a room 11 being a space to be air-conditioned, but the present invention is not limited thereto. There may be employed, for example, a ceiling concealed type. Further, the indoor unit 100 is not limited to be installed in the room 11, and may be installed, for example, in a room in a building or in a storage.

[0019] As illustrated in FIG. 2, through the upper surface 1c forming an upper portion of the indoor unit 100, an air inlet 2 for allowing indoor air to be sucked therethrough into the indoor unit 100 is formed. On a lower side of the main body 1, there are formed an air outlet 3 for allowing conditioned air to be supplied therethrough into the room, and a guide wall 10 for guiding air discharged from a cross-flow fan 8 described later into the air outlet 3.

[0020] Further, as illustrated in FIG. 2, in the upper surface 1c of the main body 1, there are arranged a filter 5 for removing, for example, dust in the air sucked through the air inlet 2, a heat exchanger 7 for transferring heating energy or cooling energy of refrigerant into air so as to generate the conditioned air, a stabilizer 9 for partitioning an air inlet-side air passage E1 and an air outlet-side air passage E2 from each other, the cross-flow fan 8 for causing the air to be sucked through the air inlet 2 and causing the air to be blown out through the air outlet 3, and vertical airflow direction vanes 4a and horizontal airflow direction vanes 4b for adjusting a direction of the air blown out of the cross-flow fan 8.

[0021] The air inlet 2 is an opening for allowing the indoor air to be forcibly sucked by the cross-flow fan 8 into the indoor unit 100. Note that, the air inlet 2 is formed only in the opening through the upper surface of the main body 1 in the example illustrated in FIG. 1 and FIG. 2, but may be formed in an opening through the front panel 1a. Further, the air inlet 2 is not particularly limited in shape.

[0022] The air outlet 3 is an opening for allowing the air, which is taken through the air inlet 2 and passes through the heat exchanger 7, to be supplied through the air outlet 3 into the room. The air outlet 3 is opened through the front panel 1a. Note that, the air outlet 3 is not particularly limited in shape.

[0023] The guide wall 10 is configured to form the air outlet-side air passage E2 cooperatively with a lower surface side of the stabilizer 9. The guide wall 10 forms a slope inclined from the cross-flow fan 8 toward the air outlet 3. It is preferred that the slope be formed so as to correspond to, for example, a part of a spiral shape.

[0024] The filter 5 is formed, for example, into a mesh-like shape to remove the dust in the air sucked through the air inlet 2. The filter 5 is arranged in an air passage from the air inlet 2 to the air outlet 3 (central portion in the main body 1), specifically, on a downstream side with respect to the air inlet 2 and on an upstream side with respect to the heat exchanger 7.

[0025] The heat exchanger 7 (indoor heat exchanger) functions as an evaporator during a cooling operation to cool the air, and functions as a condenser (radiator) during a heating operation to heat the air. The heat exchanger 7 is arranged in the air passage from the air inlet 2 to the air outlet 3 (central portion in the main body 1), specifically, on a downstream side with respect to the filter 5 and on an upstream side with respect to the cross-flow fan 8. Note that, in FIG. 2, the heat exchanger 7 is formed into a shape surrounding a front portion and an upper portion of the cross-flow fan 8, but is not particularly limited thereto.

[0026] The heat exchanger 7 is connected to an outdoor unit including a compressor, an outdoor heat exchanger, an expansion device, and the like to form a refrigeration cycle. Further, as an example of the heat exchanger 7, there is given a fin-and-tube heat exchanger of a cross fin type including heat transfer tubes and a large number of fins.

[0027] As illustrated in FIG. 2, the stabilizer 9 is arranged under the heat exchanger 7 so as to partition the air inlet-side air passage E1 and the air outlet-side air passage E2 from each other. The air inlet-side air passage E1 is formed on an upper surface side of the stabilizer 9, and the air outlet-side air passage E2 is formed on the lower surface side of the stabilizer 9. The stabilizer 9 includes a drain pan 6 for temporarily accumulating dew condensation water adhering to the heat exchanger 7.

[0028] The cross-flow fan 8 is configured to suck the indoor air through the air inlet 2, and to blow out the conditioned air through the air outlet 3. The cross-flow fan 8 is arranged in the air passage from the air inlet 2 to the air outlet 3 (central portion in the main body 1), specifically, on a downstream side with respect to the heat exchanger 7 and on an upstream side with respect to the air outlet 3.

[0029] As illustrated in FIG. 3, the cross-flow fan 8 includes an impeller 8a, a motor 12 for rotating the impeller 8a, and a motor shaft 12a for transmitting rotation of the motor 12 to the impeller 8a.

[0030] The impeller 8a is made of a thermoplastic resin such as an ABS resin, and is rotated to suck the indoor air through the air inlet 2 and send the conditioned air into the air outlet 3.

[0031] As illustrated in FIG. 3, the impeller 8a includes a plurality of impeller elements 8d coupledto each other. The impeller elements 8d each include a plurality of blades 8c and a ring 8b serving as a support plate fixed on an endportion side of the plurality of blades 8c. In other words, the impeller 8a is an integral member formed by welding and coupling the plurality of impeller elements 8d each including the plurality of blades 8c that are sequentially formed to extend substantially perpendicularly from a lateral surface of an outer peripheral portion of the disk-like ring 8b at predetermined intervals in a circumferential direction of the ring 8b.

[0032] Further, the impeller 8a includes a fan boss 8e and a fan shaft 8f. The fan boss 8e is a part projecting to an inside of the impeller 8a. The motor shaft 12a is fixed to the fan shaft 8f with a screw or the like. One side of the impeller 8a is supported by the motor shaft 12a through intermediation of the fan boss 8e, and another side of the impeller 8a is supported by the fan shaft 8f. With this, the impeller 8a can be rotated in a rotation direction RO about a rotation axis center O of the impeller 8a under a state in which both the end sides thereof are supported, and, as illustrated in FIG. 2, the impeller 8a can suck the indoor air through the air inlet 2 and send the conditioned air into the air outlet 3.

[0033] The vertical airflow direction vanes 4a are configured to adjust a vertical direction of the air blown out of the cross-flow fan 8, and the horizontal airflow direction vanes 4b are configured to adjust a horizontal direction of the air blown out of the cross-flow fan 8.

[0034] The vertical airflow direction vanes 4a are arranged on a downstream side with respect to the horizontal airflow direction vanes 4b. As illustrated in FIG. 2, the vertical airflow direction vanes 4a are mounted to the guide wall 10 so that upper portions of the vertical airflow direction vanes 4a are freely turnable.

[0035] The horizontal airflow direction vanes 4b are arranged on an upstream side with respect to the vertical airflow direction vanes 4a. As illustrated in FIG. 1, the vertical airflow direction vanes 4a are turned under a state in which both end portion sides of the vertical airflow direction vanes 4a are supported by parts that define the air outlet 3 in the main body 1.

[0036] As illustrated in FIG. 4 to FIG. 6, an outer peripheral-side end portion 15a and an inner peripheral-side end portion 15b of the blade 8c are each formed into, for example, a circular-arc shape. Further, the blade 8c is formed so that the outer peripheral-side end portion 15a is tilted forward along the impeller rotation direction RO with respect to the inner peripheral-side end portion 15b. In other words, in a vertical cross-section of the blade 8c, a pressure surface 13a and a suction surface 13b of the blade 8c are curved forward along the impeller rotation direction RO as being shifted from the rotation axis O of the impeller 8a toward an outer side of the blade 8c. Further, the blade 8c is formed into such an arcuate shape that a vicinity of a center of the blade 8c is farthest from a straight line connecting the outer peripheral-side end portion 15a and the inner peripheral-side end portion 15b to each other.

[0037] A center of a circle corresponding to the circular-arc shape formed on the outer peripheral-side end portion 15a is represented by P1 (also referred to as "circular-arc center P1") , and a center of a circle corresponding to the circular-arc shape formed on the inner peripheral-side end portion 15b is represented by P2 (also referred to as "circular-arc center P2"). Further, a line segment connecting the circular-arc centers P1 and P2 to each other is defined as a chord line L. In addition, as illustrated in FIG. 6, a length of the chord line L is represented by Lo (hereinafter also referred to as "chord length Lo").

[0038] The blade 8c has the pressure surface 13a as a surface on a forward side in the rotation direction RO of the impeller 8a, and the suction surface 13b as a surface on a rearward side in the rotation direction RO of the impeller 8a. The blade 8c is formed into a concave shape curved in a vicinity of a center of the chord line L in a direction from the pressure surface 13a toward the suction surface 13b. In other words, both the pressure surface 13a and the suction surface 13b are curved in a concavedmanner toward the rearward side in the rotation direction RO.

[0039] Further, in the blade 8c, an outer peripheral side of the impeller 8a and an inner peripheral side of the impeller 8a are different from each other in radius of a circle corresponding to a circular-arc shape on the pressure surface 13a side.

[0040] Specifically, as illustrated in FIG. 4, a surface of the blade 8c on the pressure surface 13a side includes an outer peripheral-side curved surface Bp1 having a radius (circular-arc radius) Rp1, which corresponds to a circular-arc shape on the outer peripheral side of the impeller 8a, and an inner peripheral-side curved surface Bp2 having a radius (circular-arc radius) Rp2, which corresponds to a circular-arc shape on the inner peripheral side of the impeller 8a. In this way, the surface of the blade 8c on the pressure surface 13a side is a circular-arc curved surface having a plurality of curvatures.

[0041] Further, on the surface of the blade 8c on the pressure surface 13a side, there is formed a flat surface Qp having a flat surface shape and being connected to an end portion of the inner peripheral-side curved surface Bp2 on the inner peripheral side.

[0042] In this way, the surface of the blade 8c on the pressure surface 13a side is formed of the outer peripheral-side curved surface Bp1, the inner peripheral-side curved surface Bp2, and the flat surface Qp that are connected continuously with each other.

[0043] Meanwhile, a surface of the blade 8c on the suction surface 13b side is a surface corresponding to the surface on the pressure surface 13a side. Specifically, the surface of the blade 8c on the suction surface 13b side includes an outer peripheral-side curved surface Bs1 having a radius (circular-arc radius) Rs1, which corresponds to the circular-arc shape on the outer peripheral side of the impeller 8a, and an inner peripheral-side curved surface Bs2 having a radius (circular-arc radius) Rs2, which corresponds to the circular-arc shape on the inner peripheral side of the impeller 8a.

[0044] Further, on the surface of the blade 8c on the suction surface 13b side, there is formed a flat surface Qs having a flat surface shape and being connected to an end portion of the inner peripheral-side curved surface Bs2 on the inner peripheral side.

[0045] In this way, the surface of the blade 8c on the suction surface 13b side is formed of the outer peripheral-side curved surface Bs1, the inner peripheral-side curved surface Bs2, and the flat surface Qs that are connected continuously with each other.

[0046] Specifically, in the vertical cross-section of the blade 8c, when a diameter of an inscribed circle that is tangent to the blade surfaces is defined as a blade thickness, as illustrated in FIG. 4, a blade thickness t1 of the outer peripheral-side end portion 15a is smaller than a blade thickness t2 of the inner peripheral-side end portion 15b. Note that, the blade thickness t1 is twice as large as a radius R1 of the inscribed circle at the outer peripheral-side end portion 15a, and the blade thickness t2 is twice as large as a radius R2 of a circle forming the circular arc of the inner peripheral-side end portion 15b.

[0047] In other words, when the diameter of the inscribed circle that is tangent to the pressure surface 13a and the suction surface 13b of the blade 8c is defined as the blade thickness, the blade 8c is formed so that the blade thickness is smaller at the outer peripheral-side end portion 15a than at the inner peripheral-side end portion 15b, gradually increased from the outer peripheral-side end portion 15a toward the center to become largest at a predetermined position in the vicinity of the center, gradually reduced toward the inner peripheral side, and is substantially uniform in a straight portion Q.

[0048] More specifically, within a range of the outer peripheral-side curved surfaces Bp1 and Bs1 and the inner peripheral-side curved surfaces Bp2 and Bs2 that are formed of the pressure surface 13a and the suction surface 13b except for the outer peripheral-side end portion 15a and the inner peripheral-side end portion 15b, the blade thickness of the blade 8c is gradually increased from the outer peripheral-side end portion 15a toward the center of the blade 8c, reaches a maximum thickness t3 at the predetermined position in the vicinity of the center of the chord line L, and is gradually reduced toward the inner peripheral-side end portion 15b. Then, the blade thickness is maintained substantially at a fixed value of the inner peripheral-side end portion thickness t2 within a range of the straight portion Q, specifically, a range between the flat surface Qp and the flat surface Qs.

[0049] When a part of the blade 8c, which has the flat surfaces Qp and Qs of the inner peripheral-side end portion 15b as its surfaces, is referred to as the above-mentioned straight portion Q, the suction surface 13b of the blade 8c includes a plurality of circular arcs and the straight portion Q bent therefrom, which are formed from the outer peripheral side to the inner peripheral side of the impeller.

[0050] As illustrated in FIG. 4 to FIG. 7, on each of the pressure surface 13a and the suction surface 13b, a step 16 is formed at a position between the outer peripheral-side end portion 15a and the inner peripheral-side end portion 15b in a chord direction of the blade. The step 16 is formed so that, on each of the surfaces (corresponding pressure surface 13a and corresponding suction surface 13b) of the blade, a fan inner peripheral-side part with respect to the step 16 is further projected (larger in blade thickness) than a fan outer peripheral-side part with respect to the step 16. Further, the step 16 is formed so as to extend obliquely with respect to the impeller rotation axis, and to vary (gradually increase or decrease) in height over a direction of the impeller rotation axis. More specifically, as illustrated in FIG. 7, the step 16 is formed along a step base line 16a that is inclined at a predetermined angle γ with respect to a straight line O1 parallel to the impeller rotation axis O so that the step height is gradually increased in a direction in which the step base line 16a is separated from the blade outer peripheral-side end portion 15a. With this, a pressure surface-side step height Hd1 and a suction surface-side step height Hd2 are gradually varied in a longitudinal direction of the blade.

[0051] Next, with reference mainly to FIG. 5, description is made of a relationship between maximum chord camber-lengths Lp and Ls and the chord length Lo.

[0052] First, as illustrated in FIG. 5, a tangent point between the pressure surface 13a and a parallel line Wp that is tangent to the pressure surface 13a and parallel to the chord line L is defined as a maximum camber position Mp, and a tangent point between the suction surface 13b and a parallel line Ws that is tangent to the suction surface 13b and parallel to the chord line L is defined as a maximum camber position Ms. Further, an intersection between the chord line L and a perpendicular line that is perpendicular to the chord line L and passes through the maximum camber position Mp is defined as a maximum chord camber-point Pp, and an intersection between the chord line L and a perpendicular line that is perpendicular to the chord line L and passes through the maximum camber position Ms is defined as a maximum chord camber-point Ps. Still further, a distance between the circular-arc center P2 and the maximum chord camber-point Pp is defined as the maximum chord camber-length Lp, and a distance between the circular-arc center P2 and the maximum chord camber-point Ps is defined as the maximum chord camber-length Ls. Yet further, a distance of a line segment between the maximum camber position Mp and the maximum chord camber-point Pp is defined as a maximum camber height Hp, whereas a distance of a line segment between the maximum camber position Ms and the maximum chord camber-point Ps is defined as a maximum camber height Hs. In addition, when ratios Lp/Lo and Ls/Lo between the maximum chord camber-lengths Lp and the chord length Lo and between the maximum chord camber-length Ls and the chord length Lo are set as follows, noise can be reduced.

[0053] In this case, when the maximum camber positions are located excessively on the outer peripheral side, the inner peripheral-side curved surface Bs2 becomes excessively flat. Meanwhile, when the maximum camber positions are located excessively on the inner peripheral side, the outer peripheral-side curved surface Bs1 becomes excessively flat, and the inner peripheral-side curved surface Bs2 is excessively cambered. In this way, when the blade 8c partially becomes excessively flat, or is partially excessively cambered, separation is liable to occur in the air outlet-side air passage E2. As a result, noise is worsened. As a countermeasure, in this embodiment, the blade 8c is formed so that the maximum camber positions fall within an optimum range.

[0054] First, when the ratios Ls/Lo and Lp/Lo are each less than 40%, and the maximum camber positions are located on the impeller inner peripheral side, the circular-arc radii of the inner peripheral-side curved surfaces Bs2 and Bp2 of the blade 8c are small. Further, when the circular-arc radii of the inner peripheral-side curved surfaces Bs2 and Bp2 of the blade 8c are small, the blade 8c is sharply cambered to form a steep curve. Thus, in the air outlet-side air passage E2, the air stream having passed along the flat surface Qs and the flat surface Qp through the inner peripheral-side end portion 15b cannot flow along the inner peripheral-side curved surfaces Bs2 and Bp2. As a result, the air stream is separated to cause pressure fluctuation.

[0055] Further, when the ratios Ls/Lo and Lp/Lo are each more than 50%, and the maximum camber positions are located on the impeller outer peripheral side, the circular-arc radii of the outer peripheral-side curved surfaces Bs1 and Bp1 of the blade 8c are large. Further, when the circular-arc radii of the outer peripheral-side curved surfaces Bs1 and Bp1 of the blade 8c are large, the camber of the blade 8c is small. Thus, the air streams are separated from the outer peripheral-side curved surfaces Bs1 and Bp1 of the blade 8c, with the result that trailing vortices are intensified.

[0056] Further, even in a case where the ratios Lp/Lo and Ls/Lo each fall within a range of from 40% to 50%, when the relationship of Ls/Lo>Lp/Lo is satisfied, the maximum camber position of the suction surface 13b is located closer to the outer peripheral side than that of the pressure surface 13a. With this, intervals between the adjacent blades 8c each repeatedly fluctuate from the inner peripheral-side end portion 15b toward the outer peripheral-side end portion 15a. As a result, pressure fluctuation occurs.

[0057] As a countermeasure, in this embodiment, the blade 8c is formed so as to satisfy the relationship of 40%≤Ls/Lo<Lp/Lo≤50%. With this, the air streams can be suppressed from being separated from the blade surfaces on both the air inlet side and the air outlet side of the impeller. As a result, noise can be suppressed, and electric power consumption of the fan motor can be reduced. In other words, the indoor unit 100 for the air-conditioning apparatus having mounted thereto the cross-flow fan 8 with excellent quietness and high energy efficiency can be provided.

[0058] When the maximum camber heights Hp and Hs are excessively large, the circular-arc radii of the curved surfaces may be small to cause excessively sharp cambering. Meanwhile, when the maximum camber heights Hp and Hs are excessively small, the circular-arc radii of the curved surfaces may be large to cause excessively small cambering. Further, when the intervals between the adjacent blades 8c are excessively large, the air stream cannot be controlled. As a result, separation vortices may be formed between the blade surfaces to generate fluid abnormal noise. In contrast, when the intervals are excessively small, the air velocity may be increased to generate louder noise. As a countermeasure, in this embodiment, the blade 8c is formed so that the maximum camber heights fall within an optimum range.

[0059] The reference symbols "Hp" and "Hs" respectively represent the maximum camber heights of the pressure surface 13a and the suction surface 13b, and hence the relationship of Hs>Hp is established. When ratios Hs/Lo and Hp/Lo are each less than 10%, the circular-arc radii of the curved surfaces are large to cause excessively small cambering. Thus, the intervals between the adjacent blades 8c are excessively large, and hence the air stream cannot be controlled. As a result, the separation vortices may be formed between the blade surfaces to generate the fluid abnormal noise. Finally, a noise level may be abruptly increased. In contrast, when the ratios Hs/Lo and Hp/Lo are each more than 25%, the intervals between the adjacent blades are excessively small, with the result that the air velocity may be increased to abruptly worsen noise.

[0060] As a countermeasure, in this embodiment, the blade 8c is formed so as to satisfy the relationship of 25%≥Hs/Lo>Hp/Lo≥10%. With this, the air streams can be suppressed from being separated from the blade surfaces on both the air inlet side and the air outlet side of the impeller. As a result, noise can be suppressed, and electric power consumption of the fan motor can be reduced. In other words, the indoor unit 100 for the air-conditioning apparatus having mounted thereto the cross-flow fan 8 with excellent quietness and high energy efficiency can be provided.

[0061] Next, with reference mainly to FIG. 6, description is made of a relationship between a chord length Lf of the straight portion Q and the chord length Lo.

[0062] A center of an inscribed circle that is tangent to a connection position (first connection position) between the inner peripheral-side curved surface Bp2 and the flat surface Qp and a connection position (second connection position) between the inner peripheral-side curved surface Bs2 and the flat surface Qs is represented by P4. A center line of the blade 8c, which passes between the inner peripheral-side curved surface Bp2 and the inner peripheral-side curved surface Bs2 on the outer peripheral side with respect to the straight portion Q in the blade 8c, is defined as a thickness center line Sb. Further, a straight line passing through the center P4 and the circular-arc center P2 is defined as an extending line Sf. A tangent line that is tangent to the thickness center line Sb at the center P4 is represented by Sb1. An angle formed between the tangent line Sb1 and the extending line Sf is defined as a bending angle θe. In addition, a distance between a perpendicular line that is perpendicular to the chord line L and passes through the circular-arc center P2, and a perpendicular line that is perpendicular to the chord line L and passes through the center P4 is defined as a straight portion chord length Lf. A center of an inscribed circle that is tangent to a thickest portion of the blade is represented by P3. An intersection between a perpendicular line that is perpendicular to the chord line and passes through the center P3 and the chord line is represented by Pt. A distance between the perpendicular line that is perpendicular to the chord line L and passes through the center P3, and the perpendicular line that is perpendicular to the chord line L and passes through the circular-arc center P2 is defined as a thickest portion length Lt. Note that, the reference symbol βb represents a blade outlet angle.

[0063] When the chord length Lf of the straight portion Q of the inner peripheral-side end portion 15b of the blade 8c is excessively large with respect to the chord length Lo, the circular-arc radii of the outer peripheral-side curved surfaces Bp1 and Bs1 and the inner peripheral-side curved surfaces Bp2 and Bs2 on the outer peripheral side with respect to the straight portion Q are small. As a result, the blade 8c is sharply cambered. Thus, the air stream tends to be separated to increase loss and input to the fan motor. In addition, the distances between the blades 8c are each extremely changed from the inner peripheral side toward the outer peripheral side to cause pressure fluctuation. As a result, noise becomes louder.

[0064] In contrast, when the chord length Lf of the straight portion Q is excessively small with respect to the chord length Lo, that is, when the inner peripheral side of the blade is formed mostly of the curved surfaces, there arises a problem in that negative pressure is not generated on the suction surface 13b after the air stream impinges on the inner peripheral-side end portion 15b, and hence the air stream is separated without being re-adhered to cause louder noise. In particular, when airflow resistance is increased by a large amount of dust accumulated on the filter 5, such a problem conspicuously occurs.

[0065] In view of this problem, investigations by the inventers of the present invention have demonstrated that the increase in input to the fan motor can be suppressed when a ratio Lf/Lo is 30% or less, and the increase in noise can also be suppressed when the ratio Lf/Lo is 5% or more and 30% or less.

[0066] Thus, in this embodiment, the blade 8c is formed so as to satisfy the relationship of 30%≥Lf/Lo≥5%. With this, the air streams can be suppressed frombeing separated from the blade surfaces on both the air inlet side and the air outlet side of the impeller. As a result, noise can be suppressed, and electric power consumption of the fan motor can be reduced. In other words, the indoor unit 100 for the air-conditioning apparatus having mounted thereto the cross-flow fan 8 with excellent quietness and high energy efficiency can be provided.

[0067] In this embodiment, the blade formed as described above provides advantages as described below.

(1) When the blade 8c passes through the air inlet-side air passage E1 and the air stream along the blade surface is almost separated from the outer peripheral-side curved surface Bs1, the inner peripheral-side curved surface Bs2 having a different circular-arc radius causes the air stream to be re-adhered.

(2) Further, the blade 8c has the flat surface Qs to generate negative pressure. Thus, even when the air stream is almost separated from the inner peripheral-side curved surface Bs2, the air stream is re-adhered.

(3) Still further, the blade thickness is larger on the impeller inner peripheral side than on the impeller outer peripheral side, and hence the distances between the adjacent blades 8c in the circumferential direction are reduced.

(4) Yet further, the flat surface Qs is flat, and hence the blade thickness is not abruptly increased toward the impeller inner periphery in comparison with a case of a curved surface. With this, frictional resistance can be suppressed.

(5) The pressure surface 13a of the blade 8c is also formed of the plurality of circular arcs and the straight portion (flat surface) from the outer peripheral side toward the inner peripheral side of the impeller. Thus, when the air flows from the outer peripheral-side curved surface Bp1 to the inner peripheral-side curved surface Bp2 having a different circular-arc radius, the air stream is gradually accelerated. Thus, a pressure gradient is generated along the suction surface 13b. With this, separation is suppressed, and hence fluid abnormal noise is not generated.

(6) Further, the flat surface Qp on a downstream side is a tangent line that is tangent to the inner peripheral-side curved surface Bp2. In other words, the blade 8c has the flat surface Qp on the downstream side, and hence is formed into a shape bent at a predetermined angle with respect to the rotation direction RO. Thus, in comparison with a case where a straight surface (flat surface Qp) is not formed, when the blade thickness t2 of the inner peripheral-side end portion 15b is large, the air stream can be directed to the suction surface 13b. With this, a trailing vortex can be suppressed when the air stream flows to the inside of the impeller through the inner peripheral-side end portion 15b.

(7) The blade 8c is thickened at the inner peripheral-side end portion 15b, and hence separations in various inflow directions in the air outlet-side air passage E2 are less likely to occur.

(8) Further, the blade 8c is thickest in the vicinity of the center of the chord on a downstream side with respect to the flat surface Qs. Thus, when the air stream is almost separated after passing along the flat surface Qs, the air stream flows along the inner peripheral-side curved surface Bs2 because the blade thickness is gradually increased toward the vicinity of the center of the chord along the inner peripheral-side curved surface Bs2. Thus, the air stream can be suppressed from being separated.

(9) Still further, the blade 8c has the inner peripheral-side curved surface Bp2 having a different circular-arc radius, which is formed on a downstream side with respect to the inner peripheral-side curved surface Bs2. With this, the separation of the air stream is suppressed, and hence an effective air outlet-side air passage from the impeller can be enlarged. As a result, an outlet air velocity can be reduced and uniformized, and load torque applied to the blade surfaces can be reduced.

(10) The blade 8c is formed so that the circular-arc radii Rp1, Rp2, Rs1, and Rs2 satisfy the following relationship in degrees. Specifically, the blade 8c is formed to satisfy the relationship of Rs1>Rp1>Rs2>Rp2. With this, on the suction surface 13b, the circular-arc radius Rs1 of the outer peripheral-side curved surface Bs1 is larger than the circular-arc radius Rs2 of the inner peripheral-side curved surface Bs2, and the suction surface 13b is formed into a somewhat flat circular arc having a small curvature. Thus, in the air outlet-side air passage E2, the air stream flows along the outer peripheral-side curved surface Bs1 up to the vicinity of the outer peripheral-side end portion 15a thereof, and hence the trailing vortex can be reduced. Further, on the pressure surf ace 13a, the circular-arc radius Rp1 of the outer peripheral-side curved surface Bp1 is larger than the circular-arc radius Rp2 of the inner peripheral-side curved surface Bp2, and the pressure surface 13a is formed into a somewhat flat circular arc having a small curvature. Thus, the air stream gently flows without being biased on the pressure surface 13a side. With this, friction loss can be reduced.

(11) On each of the pressure surface 13a and the suction surface 13b, the step 16 is formed at a position located at a predetermined distance from the outer peripheral-side end portion 15a to the center of the chord in the chord direction of the blade. The step 16 has such a shape that the fan inner peripheral side is projected further to an outside of the blade surface than on the fan outer peripheral side. The step 16 is formed at a position where the predetermined angle γ is formed with respect to the impeller rotation axis O (straight line O1 parallel to the rotation axis O). Further, the height of the step 16 is gradually increased over the longitudinal direction of the blade. Thus, with regard to the air velocity variation that may occur on the fan air inlet side and the fan air outlet side during rotation of the fan, on the fan air inlet side, even when the air stream is almost separated from the suction surface 13b, the step is projected in the thickness direction, and hence the air stream is re-adhered, to thereby suppress the separation. On the pressure surface 13a, the step 16 is formed at the predetermined angle γ with respect to the impeller rotation axis O. Thus, even when the air stream along the blade surface reaches the step 16, pressure concentration of the air stream in the chord direction can be avoided. In addition, even when the air stream is significantly separated from the suction surface and almost drifted onto the pressure surface, the step causes the air stream to be forced down onto an adjacent suction surface. With this, the separation can be suppressed. Further, on each of the suction surface 13b and the pressure surface 13a on the fan air outlet side, even when the air stream is almost separated toward a downstream side, negative pressure is generated at the step 16. With this, the air streams flow along the blade surfaces, and hence the separation is suppressed. Thus, an effective flow passage width between the blades is increased, with the result that loss is reduced. In addition, the height of the step 16 is gradually increased over the direction of the impeller rotation axis. Thus, pressure concentration on the step 16 varies over the direction of the impeller rotation axis. With this, even when the air streams are almost separated, the air streams are re-adhered to the blade surfaces.

[0068] As described above, the air streams can be suppressed from being separated from the blade surfaces on both the air inlet side and the air outlet side of the impeller. Thus, noise can be suppressed, and electric power consumption of the fan motor can be reduced. In other words, the indoor unit 100 having mounted thereto the cross-flow fan 8 with excellent quietness and high energy efficiency can be provided.

Second Embodiment

[0069] Next, description is made of a second embodiment of the present invention. FIG. 8 is a view for illustrating the second embodiment of the present invention in the same manner as that of FIG. 7. Note that, except for the parts described below, the second embodiment is similar to the first embodiment described above.

[0070] As illustrated in FIG. 8, a blade 8c' of an impeller according to the second embodiment has a step 16' including a plurality of projections and recesses that are formed forward to the blade outer peripheral side and rearward therefrom along the direction of the chord L continuously over the direction of the impeller rotation axis. In other words, the step 16' includes projections and recesses that are formed along the blade surface to be projected and recessed in a direction orthogonal to the longitudinal direction of the blade (direction parallel to the impeller rotation axis). Further, those projections and recesses are formed of acute peaks and valleys that are alternately arrayed along a step base line 16a'.

[0071] The step 16' formed as described above provides such a function that, even when the air stream is almost separated at the step, a longitudinal vortex generated by the projections and the recesses forces down the air stream onto the blade surface. With this, the effective flow passage between the blades is enlarged to reduce airflow resistance between the blades, and hence passage loss is reduced. Thus, the load torque is reduced, with the result that electric power consumption of the fan motor is reduced. In this way, an indoor unit for an air-conditioning apparatus with high energy efficiency can be provided.

Third Embodiment

[0072] Next, description is made of a third embodiment of the present invention. FIG. 9 is a view for illustrating the third embodiment of the present invention in the same manner as that of FIG. 7. FIG. 10 is a view for illustrating a state of the blade of FIG. 9 when viewed along an extension direction of the outer peripheral-side end portion, that is, when viewed along the arrow X in FIG. 6.

[0073] In the first embodiment and the second embodiment described above, the step 16 is formed along the step base line 16a forming the predetermined angle γ with respect to the straight line O1 parallel to the impeller rotation axis O, and the step 16' includes the projections and the recesses that are formed alternately along the step base line 16a. The heights of those steps 16 and 16' are gradually increased over the longitudinal direction of the blade. The present invention is not limited thereto, and includes such a mode that the height of the step is increased and reduced over the longitudinal direction. FIG. 9 and FIG. 10 are illustrations of an example of such a mode, in particular, a mode that the step includes convex portions and concave portions formed alternately along the step base line, and that the height of the step is increased and reduced over the longitudinal direction.

[0074] As illustrated in FIG. 9 and FIG. 10, a step 16" is formed in such a mode that a plurality of convex portions and a plurality of concave portions are formed forward and rearward in the direction of the chord L continuously over the direction of the impeller rotation axis. Further, a forward amount and a rearward amount of the convex portions and the concave portions become larger as a position of the step approaches to one side in the longitudinal direction of the blade. In addition, a height of the step 16" is increased or reduced over the longitudinal direction of the blade. More specifically, an increasing rate of the height of the step 16" becomes higher as the position of the step approaches to one side in the longitudinal direction of the blade.

[0075] Also in such a mode, the step is formed at the predetermined angle δ with respect to the impeller rotation axis O. Thus, even when the air stream along the blade surface reaches the step, the pressure concentration of the air stream in the chord direction can be avoided. In addition, even when the air stream is significantly separated from the suction surface and almost drifted onto the pressure surface, the step causes the air stream to be forced down onto an adjacent suction surface. With this, the separation can be suppressed. Note that, the mode in the illustration corresponds to an example in which the height of the step of the second embodiment is increased and reduced over the longitudinal direction, but the third embodiment may also be carried out in such a mode that the height of the step of the first embodiment is increased and reduced over the longitudinal direction.

Fourth Embodiment

[0076] Next, description is made of a fourth embodiment of the present invention. FIG. 11 is a view for illustrating the fourth embodiment of the present invention in the same manner as that of FIG. 3. FIG. 12 is a view for illustrating cross-sections taken along the line A-A, the line B-B, and the line C-C in FIG. 11 in a superimposed manner. FIG. 13 is a perspective view of the blade of the impeller of FIG. 11 when viewed from the pressure surface side. Note that, in FIG. 12, hatching is omitted for the sake of clarity of illustration of the inside between the blade surfaces. Further, except for the parts described below, the fourth embodiment is similar to the first embodiment described above.

[0077] As illustrated in FIG. 11 and FIG. 13, a blade 108c according to the fourth embodiment is roughly divided into three regions along a width in a longitudinal direction of the blade 108c. Those three regions include blade ring near portions 8ca arranged on both the end portion sides adjacent to the rings 8b under a state in which the rings 8b are mounted to the impeller, a blade central portion 8cb arranged at a central portion of the blade, and blade intermediate portions 8cc arranged between the blade ring near portions 8ca and the blade central portion 8cb.

[0078] Note that, in the following description, the blade ring near portions 8ca are also referred to as first regions, the blade central portion 8cb is also referred to as a second region, and the blade intermediate portions 8cc are also referred to as third regions.

[0079] Further, as illustrated in FIG. 13, at portions between the first regions and the third regions, coupling portions 8g that are curved in conformity with a concave shape of the blade 108c are formed as first coupling portions. In other words, the first regions and the third regions are connected to each other with the coupling portions 8g.

[0080] Further, at portions between the third regions and the second region, coupling portions 8g that are curved in conformity with the concave shape of the blade 108c are formed as second coupling portions. In other words, the third regions and the second region are connected to each other with the coupling portions 8g.

[0081] Note that, when viewed along the longitudinal direction of the blade 108c, the coupling portions 8g are each inclined from a region on one side toward a region on another side. In other words, as illustrated in FIG. 13, the coupling portions 8g are inclined not only in a transverse direction in conformity with the concave shape of the blade 108c, but also in the longitudinal direction.

[0082] More specifically, as illustrated in FIG. 13, the coupling portions 8g are inclined so that the third regions are arranged on a recessed side in the blade rotation direction with respect to the first regions. In other words, the coupling portions 8g are inclined so that the third regions are located on the depth side in the drawing sheet with respect to the first regions. Further, the coupling portions 8g are inclined so that the third regions are arranged on the recessed side in the blade rotation direction with respect to the second region. In other words, the coupling portions 8g are inclined so that the third regions are located on the depth side in the drawing sheet with respect to the second region.

[0083] The components of the blade 108c are sequentially arranged along its longitudinal direction as described below.

[0084] Specifically, the blade 108c includes the components in the following order, that is, the ring 8b serving as a support plate on one side, the blade ring near portion 8ca on the one side, the coupling portion 8g, the blade intermediate portion 8cc on the one side, the coupling portion 8g, the blade central portion 8cb, the coupling portion 8g, the blade intermediate portion 8cc on another side, the coupling portion 8g, the blade ring near portion 8ca on the another side, and the ring 8b serving as a support plate on the another side. The blade 108c includes the five regions and the four coupling portions 8g between the rings 8b on both the end portion sides.

[0085] Further, over a distance WL between the two rings, the blade ring near portions 8ca, the blade central portion 8cb, and the blade intermediate portions 8cc of the blade 108c according to the fourth embodiment are formed into the same shape in the longitudinal direction respectively within regions having predetermined lengths WL1, WL2, and WL3. Note that, the reference symbol WL4 represents a blade length in each of the coupling portions.

[0086] In FIG. 12 in which the cross-section A-A, the cross-section B-B, and the cross-section C-C in FIG. 11 are superimposed on each other, the blade ring near portions 8ca, the blade central portion 8cb, and the blade intermediate portions 8cc are substantially equal to each other in outer diameters Ro of straight lines O-P1 connecting the impeller rotation center O and the circular-arc centers P1 of the outer peripheral-side end portions 15a in the circular-arc shape of the blade 108c. Thus, a diameter of a circumscribed circle of all the blades, that is, a radius of an effective impeller outer diameter is substantially uniform over the longitudinal direction. In other words, when the vertical cross-sections of the blade 108c are viewed one after another along the direction of the impeller rotation axis, values of the outer diameters Ro in the vertical cross-sections are substantially equal to each other.

[0087] Further, it can also be interpreted that the blade 108c according to the fourth embodiment is formed so that, in each of the blade cross-sections that are orthogonal to the impeller rotation axis of the cross-flow fan 8, an outer diameter corresponding to a line segment connecting the impeller rotation axis and the outer peripheral-side end portion 15a of the blade 108c to each other is substantially uniform from the one end portion side to the another end portion side in the longitudinal direction corresponding to the direction of the impeller rotation axis.

[0088] In this way, in the longitudinal direction corresponding to the direction of the impeller rotation axis of the cross-flow fan 8, the outer diameter of the outer peripheral-side end portion 15a of the blade 108c is substantially uniform in the blade sectional views that are orthogonal to the impeller rotation axis. Thus, unlike related-art blade shapes that are uneven in outer diameter over the direction of the impeller rotation axis, leakage of the air stream around the stabilizer for partitioning an air inlet region and an air outlet region of the impeller from each other can be suppressed. As a result, higher efficiency can be achieved.

[0089] In this context, description is made of the blade outlet angle.

[0090] When the thickness center line between the pressure surface 13a and the suction surface 13b of the blade 108c is defined as a camber line Sb, an outer part of the camber line Sb with respect to a predetermined radius R03 from the impeller rotation center O can be defined as an outer peripheral-side camber line S1a, and an inner part of the camber line with respect to the predetermined radius R03 from the impeller rotation center O can be defined as an inner peripheral-side camber line Sa2.

[0091] Further, a single tangent line that is tangent to a circle formed around the impeller rotation center O and passes through the circular-arc center P1 of the outer peripheral-side end portion 15a of the blade 108c can be drawn at the circular-arc center P1. The blade outlet angle refers to a narrow angle formed between this tangent line and the outer peripheral-side camber line S1a.

[0092] As illustrated in FIG. 12, a blade outlet angle defined in each of the first regions (blade ring near portions 8ca) is represented by βb1, a blade outlet angle defined in the second region (blade central portion 8cb) is represented by βb2, and a blade outlet angle defined in each of the third regions (blade intermediate portions 8cc between the blade ring near portions 8ca and the blade central portion 8cb) is represented by βb3.

[0093] In this embodiment, the first regions (blade ring near portions 8ca), the second region (blade central portion 8cb), and the third regions (blade intermediate portions 8cc between the blade ring near portions 8ca and the blade central port ion 8cb) are different from each other in blade outlet angle. In other words, values of the blade outlet angles βb1, the blade outlet angle βb2, and the blade outlet angles βb3 are set unequal to each other.

[0094] Further, it is preferred that an outer peripheral side of the blade central portion 8cb be shaped more forward in the impeller rotation direction RO than any other regions, and that, in contrast, an outer peripheral side of each of the blade intermediate portions 8cc be rearmost. The outer peripheral-side end portion 15a has a blade cross-sectional shape that is recessed most toward a reverse side in the rotation direction in each of the third regions, and is foremost in the rotation direction in the second region. More specifically, it is preferred that the blade outlet angle βb1, the blade outlet angle βb2, and the blade outlet angle βb3 satisfy the relationship of βb2<βb1<βb3.

[0095] Still further, an angle formed between a straight line passing through the impeller rotation center O and the circular-arc center P2 of the inner peripheral-side end portion 15b of the blade 108c and the straight line passing through the impeller rotation center O and the circular-arc center P1 of the outer peripheral-side end portion 15a of the blade 108c is defined as a forward angle.

[0096] Further, as illustrated in FIG. 12, a forward angle defined in each of the first regions (blade ring near portions 8ca) is represented by δ1, a forward angle defined in the second region (blade central portion 8cb) is represented by δ2, and a forward angle defined in each of the third regions (blade intermediate portions 8cc between the blade ring near portions 8ca and the blade central portion 8cb) is represented by δ3.

[0097] The relationship of βb2<βb1<βb3, which is satisfied between the above-mentioned blade outlet angles βb, may be expressed as δ3<δ1<δ2 by using a forward angle δ instead of the blade outlet angle βb.

[0098] As described above, the blade 108c is divided into a plurality of regions in the longitudinal direction between the pair of support plates, specifically, divided into the first regions at both the end portions adjacent to the support plates under the state in which the support plates are mounted to the impeller, the second region at the blade central portion, and the third regions located on both sides of the blade central portion between the first regions and the second region. Further, the blade outlet angles and the forward angles are set to appropriate values unequal to each other in the respective regions so that separation of the air stream can be suppressed to reduce noise. With this, an energy efficient and quite indoor unit for an air-conditioning apparatus having mounted thereto a cross-flow fan that is further highly efficient and reduced in noise than those having the blade shape that is uniform over the longitudinal direction can be provided.

[0099] When the cross-flow fan has the uniform blade cross-sectional shape over the longitudinal direction, the air velocity in each of the impeller elements is distributed in a height direction of the air outlet so as to be relatively higher in the blade central portion 8cb and relatively lower in the blade ring near portions 8ca due to influence of friction loss on surfaces of the rings 8b.

[0100] Meanwhile, in the cross-flow fan 8 according to the fourth embodiment, the air velocity distribution is equalized. As described above, the blade central portion 8cb is formed at the smallest blade outlet angle βb2 (largest blade forward angle), and is projected forward in the blade rotation direction RO so that the distances between the blades are small. With this, the air streams can be suppressed frombeing excessively biased in the central portion in the longitudinal direction between the rings. Further, the blade intermediate portions 8cc are each formed at the largest blade outlet angle βb3 (smallest blade forward angle). Thus, the air is blown out relatively in a radial direction in comparison with the other regions (first regions and second region). Inaddition, the distances between the adjacent blades in the blade rotation direction RO (circumferential direction) are increased. With this, the air velocity can be reduced.

[0101] Further, the ring near portions 8ca, in which the air streams flow at a low velocity, are each formed at the small blade outlet angle βb1 (large forward angle) to reduce the distance between the blades. With this, generation of turbulence due to instability of the air streams can be prevented, and in addition, the air velocity can be increased.

[0102] In addition, the turbulence is not suppressed by forming a corrugated pattern gradually curved along the longitudinal direction at the outer peripheral-side end portion so that the air stream is diffused at the outer peripheral-side end portion. Instead, in the second embodiment, the regions are formed into rectangular shapes that respectively have predetermined uniform widths and the different blade outlet angles βb so that the blade varies in shape, to thereby adjust a blow-out direction of the impeller over the longitudinal direction. With this, the air velocity distribution toward the air outlet on a downstream side is equalized. As a result, an energy efficient and quite indoor unit for an air-conditioning apparatus having mounted thereto a cross-flow fan that is further highly efficient and reduced in noise than those having the blade shape that is uniform over the longitudinal direction can be provided.

[0103] Further, the five regions different from each other in blade outlet angle are connected to each other not with substantially perpendicular steps but with the coupling portions 8g each forming an inclined surface. With this, the air stream is not abruptly diverted on the blade surface, and hence turbulence due to the steps does not occur. Thus, the air velocity distribution is equalized in the flow direction, and hence locally-high air velocity regions are eliminated. As a result, the load torque is reduced, and hence electric power consumption of the motor can be reduced. In addition, a locally-high velocity air stream does not impinge also on the airflow direction vanes arranged on the downstream side. With this, airflow resistance is reduced, and hence the load torque can be further reduced.

[0104] Still further, the velocity of the air into the airflow direction vanes is equalized, and hence locally-high velocity regions are eliminated. With this, noise to be caused by turbulence in boundary layers between surfaces of the airflow direction vanes can also be reduced.

[0105] In this way, according to the blade shape of this embodiment, both on the outer peripheral side and the inner peripheral side of the impeller, suppression of the separation, equalization of the air velocity distribution, and the like can be further achieved. With this, a cross-flow fan that is highly efficient and reduced in noise and an energy efficient and quiet indoor unit having such a cross-flow fan mounted thereto can be provided.

[0106] In addition, the blade is formed so that, in each of the first, second, and third regions, the straight portion having a substantially uniform thickness and a flat surface is formed on the inner peripheral-side end portion 15b side, that the blade cross-sectional shape on the outer peripheral side varies over the longitudinal direction of the impeller, and that the blade cross-sectional shape of the straight portion is uniform over the longitudinal direction of the impeller. With this, negative pressure is generated on the flat surface Qs. Thus, even when the air stream is almost separated from the inner peripheral-side curved surface Bs2, the air stream is re-adhered thereto.

[0107] Further, the flat surface Qs is flat, and hence the blade thickness t is not abruptly increased toward the impeller outer periphery in comparison with the case of a curved surface. With this, frictional resistance can be suppressed.

[0108] Still further, the portion having the uniform shape is formed along the impeller axis direction. Thus, cambering that may be caused due to influence of projections and recesses in causing a resin to flow or cooling at the time of resin molding is suppressed. With this, efficiencies in assembly and manufacture can be increased.

[0109] In addition, the fourth embodiment has a feature in that the blade, which provides the advantageous effect as described above, further includes the step 16.

[0110] Specifically, as most clearly illustrated in FIG. 13, the step 16 is formed in a vicinity of a boundary between an inner peripheral-side part in which the three patterns of the first regions, the second region, and the third regions in the blade cross-section have the same shape, and an outer peripheral-side part in which the three patterns of the first regions, the second region, and the third regions in the blade cross-section have different shapes. The step 16 is formed along the step base line 16a that is inclined at the predetermined angle γ with respect to the straight line O1 parallel to the impeller rotation axis O so that the step height is gradually increased in the direction in which the step base line 16a is separated from the blade outer peripheral-side end portion 15a.

[0111] When the step 16 is formed in this way, advantages as described below can be obtained. Particularly under a state in which airflow resistance is increased by dust accumulated on the filter, in each rotation of the fan, the air velocity distribution is significantly changed on the fan air inlet side. Thus, even when the blade outlet angle is changed in the longitudinal direction, separation may occur on the blade surfaces. In order to solve such a problem, the step 16 is formed in the fourth embodiment. With this, even when the separation occurs on the suction surface, the air stream is re-adhered to the blade surface. Meanwhile, on the pressure surface, the step causes the air stream to be forced out onto the adjacent suction surface, to thereby suppress the separation. With this, the effective flow passage width between the blades is secured. Meanwhile, on the fan air outlet side, when the air stream is almost separated after passing along the inner peripheral-side end portion 15b of the blade, the step 16 generates negative pressure to cause the air stream to flow along the blade surface. After that, the outer peripheral-side end portion 15a, at which different blade outlet angles are formed, causes the air stream to be spread over the rotation direction of the fan. With this, the air stream is diffused over the entire air outlet, and hence further suppressed from being drifted. Thus, airflow resistance is reduced, and hence load torque is reduced. In this way, electric power consumption of the fan motor is reduced. As a result, an indoor unit for an air-conditioning apparatus with high energy efficiency can be provided.

[0112] Note that, the above description of the fourth embodiment is made on the premise that the step 16 described in the first embodiment is provided, but the fourth embodiment may be carried out by providing, instead of such a step 16, the step described above in the second embodiment or the step described above in the third embodiment.

[0113] Although the details of the present invention are specifically described above with reference to the preferred embodiments, it is apparent that persons skilled in the art may adopt various modifications based on the basic technical concepts and teachings of the present invention.

[0114] Specifically, in each of the first to forth embodiments described above, the step is formed on both the pressure surface and the suction surface, but the present invention may be carried out in such an embodiment that the step described above is formed on at least one of the pressure surface or the suction surface.

Reference Signs List

[0115] 1 main body, 1a upper portion of main body, 1b front panel, 2 air inlet, 3 air outlet, 4a vertical airflow direction vane, 4b horizontal airflow direction vane, 5 filter, 6 drain pan, 7 heat exchanger, 8 cross-flow fan, 8a impeller, 8b ring (support plate), 8c, 8c' , 108c blade, 8ca blade ring near portion, 8cb blade central portion, 8cc blade intermediate portion, 8d impeller element, 8e fan boss, 8f fan shaft, 8g coupling portion, 9 stabilizer, 10 guide wall, 11 room, 11a wall of room, 12 motor, 12a motor shaft, 13a pressure surface, 13b suction surface, 15a outer peripheral-side end portion, 15b inner peripheral-side end portion, 16, 16', 16" step, 16a, 16' , 16" step base line, 100 indoor unit, Bp1, Bs1 outer peripheral-side curved surface, Bp2, Bs2 inner peripheral-side curved surface, E1 air inlet-side air passage, E2 air outlet-side air passage, Hd1 pressure surface-side step height, Hd2 suction surface-side step height, Hp maximum camber height (first maximum camber height), Hs maximum camber height (second maximum camber height), L chord line, Lo chord length, Lo3 chord length in third region, Lf chord length of straight portion, Lp maximum chord camber-length (first maximum chord camber-length), Ls maximum chord camber-length (second maximum chord camber-length), Lt thickest portion length, Lt3 thickest portion length in third region, Mp maximum camber position (first maximum camber position), Ms maximum camber position (second maximum camber position), O impeller rotation axis center, P1, P2, P4, P13 center, Pp maximum chord camber-point (first maximum chord camber-point), Ps maximum chord camber-point (second maximum chord camber-point), Pt thickest portion chord point, Rp1, Rp2, Rs1, Rs2 circular-arc radius, Q straight portion, Qp, Qs flat surface, RO rotation direction, Sb thickness center line, Sb1 tangent line, Sf extending line, Wp, Ws parallel line, t1 blade thickness (outer peripheral-side end portion), t2 blade thickness (inner peripheral-side end portion), t3 maximum thickness, βb blade outlet angle, βb1 blade outlet angle of first region, βb2 blade outlet angle of second region, βb3 blade outlet angle of third region, δ blade forward angle, δ1 blade forward angle of first region, δ2 blade forward angle of second region, δ3 blade forward angle of third region, θe bending angle, γ inclined angle of step, WL1 length of blade ring near portion, WL2 length of blade central portion, WL3 length of blade intermediate portion, WL4 blade length of coupling portion

Claims

1. An indoor unit for an air-conditioning apparatus, comprising:

a main body comprising an air inlet and an air outlet;

a cross-flow fan arranged inside the main body in a rotatable manner, the cross-flow fan comprising an impeller for causing air to be taken into the main body through the air inlet and causing the air to be blown out through the air outlet; and

a stabilizer for partitioning a space inside the main body into an air inlet-side flow passage on an upstream side with respect to the cross-flow fan and an air outlet-side flow passage on a downstream side with respect to the cross-flow fan,

wherein the impeller comprises a plurality of blades,

wherein the plurality of blades each comprise, in vertical sectional view, a step formed between an outer peripheral-side end portion and an inner peripheral-side end portion of the blades on at least one of a suction surface or a pressure surface being surfaces of the blades,

wherein the step is formed so that, on the surfaces of the blades, a fan inner peripheral-side part with respect to the step is further projected than a fan outer peripheral-side part with respect to the step, and

wherein the step is formed so as to extend obliquely with respect to a rotation axis of the impeller, and to vary in height over a direction of the rotation axis of the impeller.

2. An indoor unit for an air-conditioning apparatus according to claim 1, wherein the step comprises projections and recesses that are formed along the surfaces of the blades to be projected and recessed in a direction orthogonal to a longitudinal direction of each of the blades.

3. An indoor unit for an air-conditioning apparatus according to claim 1 or 2,

wherein the impeller comprises a plurality of support plates, and the plurality of blades arranged between a corresponding pair of support plates at intervals in a circumferential direction,

wherein the blades each comprise at least apair of first regions, a second region, and at least a pair of third regions as a plurality of regions that are different from each other in blade cross-section orthogonal to the rotation axis of the impeller,

wherein the first regions respectively comprise parts that are adjacent to the support plates under a state in which the support plates are mounted to the impeller,

wherein the second region comprises a part that is arranged between the corresponding pair of first regions,

wherein the third regions are respectively arranged between the corresponding pair of first regions and between the second region and the corresponding first regions,

wherein a blade outlet angle of the first region, a blade outlet angle of the second region, and a blade outlet angle of the third region are different from each other, and

wherein the step is formed in a boundary portion between an inner peripheral-side part in which three patterns of the first regions, the second region, and the third regions in the blade cross-section have the same shape, and an outer peripheral-side part in which the three patterns of the first regions, the second region, and the third regions in the blade cross-section have different shapes.

Drawing